Add includeChangedFiles parameter to get_pull_request_by_id

[lgpearson1771]

Adds an optional includeChangedFiles parameter to the existing repo_get_pull_request_by_id tool. When set to true, it fetches the latest PR iteration and returns file-level change metadata (paths and change types) — no diffs, no file content.

GitHub Issue

Closes #958

Approach

Per @danhellem's feedback, this avoids tool bloat by extending the existing tool with a parameter rather than adding a new standalone tool.

Note: I was on vacation when the issue was closed — this PR implements the approved approach from the discussion.

Changes

• src/tools/repositories.ts — Added includeChangedFiles param; fetches latest iteration and returns changedFilesSummary with change entries, file count, and pagination info
• test/src/tools/repositories.test.ts — 7 new test cases: happy path, disabled/default, empty iterations, null iteration ID, API errors, and combo with includeLabels
• docs/TOOLSET.md — Updated parameter docs

Associated Risks

Low risk — additive change behind an opt-in flag (default: false), no change to existing behavior

✅ PR Checklist

• I have read the contribution guidelines
• I have read the code of conduct guidelines
• Title of the pull request is clear and informative
• 👌 Code hygiene
• 🔭 Telemetry added, updated, or N/A
• 📄 Documentation added, updated, or N/A
• 🛡️ Automated tests added, or N/A

🧪 How did you test it?

• All 226 repository tests pass (npx jest --testPathPatterns="repositories")
• 7 new tests cover: happy path, opt-out, default behavior, empty iterations, null iteration IDs, API error handling, and combined use with includeLabels

[lgpearson1771]

@microsoft-github-policy-service agree company="Microsoft"

[codecov-commenter]

Codecov Report

❌ Patch coverage is 82.35294% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@63f76d6). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/tools/repositories.ts	82.35%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1117   +/-   ##
=======================================
  Coverage        ?   91.28%           
=======================================
  Files           ?       18           
  Lines           ?     1881           
  Branches        ?      422           
=======================================
  Hits            ?     1717           
  Misses          ?       56           
  Partials        ?      108           

Flag	Coverage Δ
unittests	91.28% <82.35%> (?)

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