feat(agent): add GitHub Copilot as an install target

[Davidson3556]

What does this PR do?

Adds GitHub Copilot as an agent install target — the most widely-used AI coding assistant, and the biggest remaining gap in the target set.

GitHub Copilot reads path-specific custom instructions from .github/instructions/*.instructions.md (VS Code, Visual Studio, Copilot Chat), with YAML frontmatter carrying an applyTo glob. This PR installs the verification-loop skill there the same way it's installed for Cursor/Cline/Windsurf:

• Path: .github/instructions/testsprite-verify.instructions.md (+ testsprite-onboard.instructions.md).
• Frontmatter: applyTo: '**' + description. Copilot instruction files have no on-demand "model decides" mode (unlike Cursor's alwaysApply: false or Windsurf's trigger: model_decision), so always-apply is the correct idiom.
• Always-on ⇒ compact body: since applyTo: '**' injects the file into every Copilot request, the target renders the compact body (~6 KB) instead of the full ~23 KB body — the same reasoning behind windsurf's compact render, keeping the always-injected context cost small.

It slots into the existing TARGETS machinery, so agent list, setup --agent, and skill-nudge install-detection pick it up automatically.

Verified locally

$ testsprite agent install --target copilot --dir /tmp/x
$ cat /tmp/x/.github/instructions/testsprite-verify.instructions.md
---
description: TestSprite verification loop — ...
applyTo: '**'
---
...
# 6009 bytes (compact), under always-on budget

Related issue

Fixes #195

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that changes existing behavior)
• Documentation only
• Build / CI / chore

Checklist

• PR targets the main branch.
• Commits follow Conventional Commits.
• npm run lint and npm run format:check pass.
• npm run typecheck passes.
• npm test passes and coverage stays at or above the 80% gate.
• New behavior is covered by unit tests (mock-based; no network or credentials required).
• No secrets, API keys, internal endpoints, or personal data are included.
• User-facing changes are reflected in README.md / DOCUMENTATION.md.

Notes for reviewers

• Follows the exact pattern established by the merged windsurf (feat(agent): add windsurf as an install target #29) and kiro (feat(agent): add kiro as an install target #10) targets: AgentTarget union, pathFor, TARGETS, help strings, README/DOCUMENTATION, both e2e matrix guards, and the regenerated help snapshot.
• Renders through the content-integrity marker path (renderOwnFileWithMarker/buildSkillMarker), so agent status tracks copilot files like every other own-file target.
• All gates green locally: typecheck, lint, format:check, 1825 unit tests, 55 e2e.
• Scope note: I saw the "target policy settled this round" note from the windsurf/kiro/gemini triage. I'm proposing Copilot as the clear next-highest-value target (it's the single most-used assistant and unclaimed), but I'm happy to defer if the target set is closed for now — no hard feelings if this waits for a future round.

AI usage disclosure

Yes, I used AI assistance for this change — investigation, implementation, and tests. I reviewed and verified everything myself (installed the target, inspected the rendered file and its frontmatter/size, and ran the full gate suite).

Summary by CodeRabbit

• New Features

  • Added support for the new Copilot agent target across the CLI and installation flow.
  • Copilot target now renders instruction files with description and applyTo: '**'.

• Bug Fixes

  • Refreshed command help text, examples, and target listings so the supported target count and output matrix are accurate.
  • Updated backup/force behavior listings to include Copilot where applicable.

• Documentation

  • Updated README and agent onboarding docs to include Copilot in supported targets and commands.

• Tests

  • Updated unit and end-to-end tests to reflect the expanded target/skill matrix (including Copilot).

[coderabbitai]

Walkthrough

This PR adds copilot as a new agent install target. It extends the AgentTarget type and TARGETS registry with own-file, compact-body rendering and YAML frontmatter, and updates CLI help, docs, and tests to reflect the expanded target matrix.

Changes

Copilot agent target support

Layer / File(s)	Summary
Copilot target type, wrapper, and registry src/lib/agent-targets.ts	Adds 'copilot' to the AgentTarget union, introduces wrapCopilot to render YAML frontmatter with description and applyTo: '**', adds a pathFor case for .github/instructions/<skill>.instructions.md, and registers a copilot entry in TARGETS as experimental, own-file, compact-body.
Unit test coverage for copilot target src/lib/agent-targets.test.ts	Expands TARGETS key/experimental/own-file assertions to include copilot, adds a renderForTarget("copilot") suite for frontmatter and compact-body validation, and updates compact-body exclusions.
CLI help text and command tests src/commands/agent.ts, src/commands/agent.test.ts	Updates help text for the agent command and --target option to list copilot, and updates runList/runInstall test expectations (target lists, row counts, would-write line counts).
End-to-end matrix and content-integrity checks test/e2e/agent-install.e2e.test.ts, test/e2e/setup.e2e.test.ts	Adds copilot frontmatter assertions for verify/onboard skills, updates JSON row-count comments, and adds copilot to matrix coverage guard target lists.
Documentation updates DOCUMENTATION.md, README.md	Adds copilot to supported target lists, install examples, target counts, and force/backup behavior descriptions.

Estimated code review effort: 2 (Simple) | ~15 minutes

Possibly related issues

• [Hackathon] Add GitHub Copilot as an agent install target #195: Matches the same Copilot agent-install target and own-file instruction rendering change set.

Possibly related PRs

• TestSprite/testsprite-cli#10: Both extend the shared AgentTarget/TARGETS matrix and adjust target-count assertions for a new coding agent target.
• TestSprite/testsprite-cli#29: Both add a new own-file agent target with matching registry, rendering, and test updates.
• TestSprite/testsprite-cli#177: Both touch agent-targets.ts rendering/wrapping behavior for own-file agent instructions.

Suggested reviewers: ruili-testsprite, zeshi-du

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The implementation adds a copilot install target with .github/instructions output, compact body, frontmatter, and TARGETS integration as requested.
Out of Scope Changes check	✅ Passed	The changes shown are all directly tied to the Copilot target feature, including docs, help text, tests, and TARGETS updates.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and accurately summarizes the main change: adding GitHub Copilot as an install target.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

src/lib/agent-targets.ts (1)

153-165: 🗄️ Data Integrity & Integration | 🔵 Trivial | ⚡ Quick win

Unquoted description in YAML frontmatter risks breaking Copilot parsing.

wrapCopilot interpolates description raw (description: ${description}) with no quoting. If the skill description ever contains a colon, leading special character, or other YAML-significant sequence, this frontmatter becomes invalid YAML — a documented failure mode where GitHub Copilot (and other tools using this pattern, like YAML-based skill loaders) will silently skip or fail to parse the file. This mirrors the same unquoted pattern already in wrapWindsurf (line 150), so it's not a new class of bug, but it doubles the exposed surface.

🛡️ Proposed fix: quote the description

 function wrapCopilot(_name: string, description: string, body: string): string {
-  return `---\ndescription: ${description}\napplyTo: '**'\n---\n\n${body}\n`;
+  return `---\ndescription: ${JSON.stringify(description)}\napplyTo: '**'\n---\n\n${body}\n`;
 }

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/lib/agent-targets.ts` around lines 153 - 165, The YAML frontmatter
generated by wrapCopilot is writing description unquoted, which can break
parsing when the text contains YAML-significant characters. Update wrapCopilot
so the description field is safely quoted/escaped before interpolation,
following the same pattern used for other instruction generators in this module,
and keep the existing applyTo and body formatting unchanged.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/commands/agent.ts`:
- Line 1064: The top-level agent command description is missing Kiro even though
it is a supported target. Update the description string in agent.ts where the
agent command metadata is defined so it matches the --target help text and docs
by including Kiro alongside the other supported editors/tools. Keep the wording
aligned with the existing list in the agent command definition.

---

Nitpick comments:
In `@src/lib/agent-targets.ts`:
- Around line 153-165: The YAML frontmatter generated by wrapCopilot is writing
description unquoted, which can break parsing when the text contains
YAML-significant characters. Update wrapCopilot so the description field is
safely quoted/escaped before interpolation, following the same pattern used for
other instruction generators in this module, and keep the existing applyTo and
body formatting unchanged.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: b3efd0a7-3675-49de-ab25-396b1f6c3be4

📥 Commits

Reviewing files that changed from the base of the PR and between b9e9601 and f839518.

⛔ Files ignored due to path filters (1)

• test/__snapshots__/help.snapshot.test.ts.snap is excluded by !**/*.snap, !**/*.snap

📒 Files selected for processing (8)

• DOCUMENTATION.md
• README.md
• src/commands/agent.test.ts
• src/commands/agent.ts
• src/lib/agent-targets.test.ts
• src/lib/agent-targets.ts
• test/e2e/agent-install.e2e.test.ts
• test/e2e/setup.e2e.test.ts

[zeshi-du]

Reviewed: scoped, tests included, CI green across the matrix.