Add test for extra ignore patterns

[sathvika234567]

Summary

Checklist

• Tests added or updated for every new or fixed behaviour
• npm test passes locally
• npm run typecheck and npm run lint pass without errors
• README updated if this change affects a documented tool, parameter, or default
• No performance budget regressions (tests/performance/ budgets still pass)

Notes for reviewer

[Juanmidev1]

Thanks for the PR — nice work with the mkdtempSync isolation and the
finally cleanup block, and good to see CI passing on all Node versions.

One thing missing before this is complete: the issue asked to verify
extraIgnorePatterns across all three tools (get_project_tree,
search_codebase, and get_project_index), and this PR only covers
get_project_tree. Could you add the same check for the other two
handlers? You should be able to reuse the same tmpRoot fixture for all
three assertions.

[sathvika234567]

Thanks for the review! I'll add equivalent integration tests for search_codebase and get_project_index and update the PR.

[Juanmidev1]

Hi Sathvika! Just checking in — no rush at all, but wanted to see if
you're still planning to add the search_codebase and get_project_index
tests we discussed. Let me know if you need any help or if you'd
prefer I pick it up from here.

[sathvika234567]

Hi! Thanks for checking in. Sorry for the delay—I got a bit busy this week. I'm still planning to add the search_codebase and get_project_index integration tests and will work on them soon. Thanks for your patience!