Add ginkgolinter to golangci-lint configuration

[JAORMX]

Summary

This PR adds the ginkgolinter to our golangci-lint configuration to ensure better code quality and consistency in our Ginkgo test suites.

Changes

Configuration Updates

• Added ginkgolinter to the enabled linters list in .golangci.yml
• Configured ginkgolinter with appropriate settings:
  • Enabled focus container detection to prevent accidentally committed focused tests
  • Enabled async interval validation for proper timeout/polling configuration
  • Kept default settings for assertion style checks

Code Fixes

• Fixed existing ginkgolinter issues in e2e tests:
  • test/e2e/group_list_e2e_test.go: Changed Expect(len(testGroups)).To(Equal(len(mixedGroupNames))) to Expect(testGroups).To(HaveLen(len(mixedGroupNames)))
  • test/e2e/stdio_proxy_over_streamable_http_mcp_server_test.go: Changed Expect(len(responses)).To(Equal(2)) to Expect(responses).To(HaveLen(2))

Benefits

The ginkgolinter helps us:

• Catch common mistakes in Ginkgo tests (e.g., function calls in async assertions)
• Enforce consistent assertion styles (e.g., using HaveLen() instead of checking len() with Equal())
• Prevent focus containers from being accidentally committed
• Ensure proper error handling patterns in tests
• Validate async assertion intervals

Testing

• Ran task lint - all checks pass
• Verified ginkgolinter is properly configured and working
• Fixed all existing ginkgolinter issues in the codebase

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46.93%. Comparing base (3a73947) to head (1ccd5c2).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1956      +/-   ##
==========================================
- Coverage   47.00%   46.93%   -0.08%     
==========================================
  Files         223      223              
  Lines       27679    27679              
==========================================
- Hits        13011    12990      -21     
- Misses      13670    13694      +24     
+ Partials      998      995       -3     

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