Remove typedoc from cli-kit (drop unused API-docs generation)

[amcaplan]

What & why

typedoc is a dev/doc-only devDependency in @shopify/cli-kit whose only consumer is an API-docs generator (packages/cli-kit/scripts/build-api-docs.js). A Round-1 investigation found the generated API docs are unlinked and unindexed, and normal PR / main / release CI never invoke typedoc. The dependency nonetheless drives recurring Dependabot churn — 35 version bumps over the last 24 months. This PR removes typedoc and its unused API-docs generation pipeline.

⚠️ Capability removal — please confirm

This PR removes the cli-kit API-docs (TSDoc) generation capability. The docs it produced were unlinked/unindexed, so we believe nothing depends on them — but if those generated API docs ARE wanted, please object here and we'll restore the pipeline. The hand-written docs published to GitHub Pages (docs/cli/*, docs/cli-kit/*, docs/decision-record/*) are NOT affected — pages.yml still builds and deploys them.

What is removed

• typedoc devDependency from packages/cli-kit/package.json (+ pnpm-lock.yaml refresh).
• packages/cli-kit/scripts/build-api-docs.js — the sole typedoc importer.
• The build-api-docs and open-api-docs nx targets (packages/cli-kit/project.json) and the matching cli-kit package.json scripts.
• The root build-api-docs script + the now-stale docs/api/cli-kit/**/*.js knip entry (and the now-stale open knip ignoreBinaries entry for cli-kit, which only the removed open-api-docs command used).
• The "Build TSDoc docs" step in .github/workflows/pages.yml, plus the packages/cli-kit/package.json push-path trigger (its sole purpose was triggering typedoc regen). Jekyll build + GitHub Pages deploy of the hand-written ./docs site are kept fully intact.

Validation (local, on this branch)

• pnpm --filter @shopify/cli-kit build → ✅ green
• pnpm --filter @shopify/cli-kit type-check → ✅ green
• pnpm --filter @shopify/cli-kit lint → ✅ green
• pnpm knip → ✅ exit 0 (no new findings)
• pnpm --filter @shopify/cli-kit exec vitest run → 1408 passed, 2 skipped. 4 failures in base-command.test.ts > removeDuplicatedPlugins are pre-existing on main (verified against a clean tree) and unrelated to this change, which touches no source/test files.
• Repo-wide grep for typedoc / build-api-docs / open-api-docs / TypeDoc → no matches.

Changeset

None — removing a devDependency is invisible to consumers of the published package (devDeps are stripped on publish), and no CI gate requires one.

🤖 Automated dependency-removal initiative — AI-generated draft, needs human review.