fix: include PR titles in generated task names

[MattPua]

Problem

Tasks created from existing GitHub PRs get generic names that omit the PR title.

Changes

• Tell task-name generation to include the existing PR number and title
• Add regression coverage for the generation prompt

How did you test this?

• pnpm exec vitest run packages/core/src/sessions/titleGeneratorService.test.ts
• pnpm typecheck
• pnpm exec prettier --check packages/core/src/sessions/titleGeneratorService.ts packages/core/src/sessions/titleGeneratorService.test.ts

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

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Created with PostHog Code

[trunk-io]

😎 Merged successfully - details.

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 6267549.}

[greptile-apps]

Prompt To Fix All With AI

### Issue 1
packages/core/src/sessions/titleGeneratorService.ts:43
**PR title corrupts summary framing**

When an existing PR title contains `SUMMARY:`, the new verbatim-copy rule places that delimiter inside the generated `TITLE:` line. The unanchored summary parser then starts inside the PR title, causing malformed conversation-summary context to be stored and used for later commit and PR generation.

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For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "fix: include PR titles in generated task..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (2): Last reviewed commit: "fix: anchor generated summary parsing" | Re-trigger Greptile}