Add PR Summary Generation with File Diffs and Messages

[bstanga]

Implements functionality to generate comprehensive PR summaries by analyzing file changes, commit messages, and PR metadata. The system processes file diffs, formats them for display, and generates both initial and walkthrough messages for pull requests.

[bstanga]

📖 Walkthrough

Implements functionality to generate comprehensive PR summaries by analyzing file changes, commit messages, and PR metadata. The system processes file diffs, formats them for display, and generates both initial and walkthrough messages for pull requests.

Changes

File	Summary
src/diff.ts	New module implementing file diff parsing and formatting. Includes functions to handle hunks, line numbers, and diff visualization with parseFileDiff, formatFileDiff, and generateFileCodeDiff utilities.
src/messages.ts	New module with buildInitialMessage and buildWalkthroughMessage functions to generate formatted PR analysis messages with file changes, commit info, and summary tables.
src/prompts.ts	Modified file structure to use new diff types and integrated formatFileDiff for better file change representation in prompts.
src/pull_request.ts	Enhanced PR handling to generate and post summaries, including initial analysis message, walkthrough generation, and automatic PR title/description updates.