fix: MCP error because types are not enforced.

[another-rex]

Fixes #2421

Also:

• fixes schema validation issue which could appear if there is additional data in database specific.
• adds integration tests to confirm all the tools works correctly.
• Add GOTOOLCHAIN default to run_lints.sh to allow linter to run when system go version is older than expected.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.68%. Comparing base (5f791d7) to head (d64b233).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/osv-scanner/mcp/command.go	0.00%	21 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2422      +/-   ##
==========================================
- Coverage   67.80%   67.68%   -0.13%     
==========================================
  Files         172      172              
  Lines       13318    13336      +18     
==========================================
- Hits         9030     9026       -4     
- Misses       3574     3594      +20     
- Partials      714      716       +2     

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[cuixq]

is this intended? this will probably override the environment variable specified in a command.

[another-rex]

This is intended, though good point about it overriding, fixed now. Right now on our machines run_lint script won't work because it uses the system's go version rather than the projects go version.

[cuixq]

this is redundant now?

[another-rex]

Ah good point, removed.

[another-rex]

/gemini review

[gemini-code-assist]

Code Review

This pull request effectively addresses a type safety issue in the MCP command by replacing sync.Map with a standard map protected by an RWMutex. This is a great improvement for correctness and maintainability. The addition of comprehensive integration tests is also a valuable contribution that significantly improves confidence in the MCP functionality. The changes to the build scripts are also sensible. I have one suggestion to improve the concurrency handling in the vulnerability cache to prevent a potential race condition during cache misses.