fix(summarize): constrain hunk summary prompts

[cursor]

Summary

Fixes ENG-517

• Clarifies summary prompts that model inputs are patch hunks, not necessarily full-file/full-diff context.
• Instructs the model to summarize only visible hunk evidence and avoid guessing broader intent.
• Adds a prompt regression test that keeps the hunk-scope guardrails in single, new-group, and evolved-group summary prompts.

Test Plan

• Attempted: cargo +stable test --locked --manifest-path apps/native/src-tauri/Cargo.toml summarize::build_prompt::tests::summary_prompts_include_hunk_scope_guardrails
• Blocked by existing Tauri test-target compile errors unrelated to this change: missing hidden_title/RunEvent::Reopen APIs, bool dereference in main.rs, and an unused variable denied in peek.rs.
• Environment setup required installing current stable Rust plus Linux Tauri deps before reaching those existing compile errors.

Docs

• No docs update needed

  

[github-actions]

	Warnings
⚠️	PR is marked WIP / draft — do not merge until ready for review.
⚠️	Please assign this PR to someone (usually yourself).

📋 PR Overview

Lines changed	40 (+39 / -1)
Files	0 added, 5 modified, 0 deleted
Draft / WIP	yes
Has Test Plan	yes
New UI components	no
New Storybook stories	no
New Rust modules	no
New TS source files	no
New tests	no
package.json touched	no
Cargo.toml touched	no
Infra / CI touched	no

🔬 Coverage

Report	Lines	Statements	Functions	Branches
apps/native/coverage/coverage-summary.json	17.9%	17.9%	31.0%	54.1%

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