feat: add since and until date filters to list_commits

[quiloos39]

Summary

Add optional since and until date filter parameters to the list_commits tool, mapping to the existing GitHub Commits API query parameters that were previously unused.

Why

When using the GitHub MCP server to analyze commit history within a specific time period (e.g., calculating working hours or reviewing activity), the tool currently returns all commits without date filtering, consuming unnecessary context window space.

What changed

• Added since and until schema properties with ISO 8601 format description to list_commits tool
• Added parameter parsing with RFC3339 date validation and user-friendly error messages
• Passed parsed times to github.CommitsListOptions
• Updated toolsnap and generated docs

MCP impact

• No tool or API changes
• Tool schema or behavior changed — two new optional input parameters (since, until) added to list_commits
• New tool added

Prompts tested (tool changes only)

• "List all commits in this repo from the last week"
• "Show me commits between January 1 and January 31, 2025"
• "What commits were made after 2025-06-01?"

Security / limits

• No security or limits impact
• Auth / permissions considered
• Data exposure, filtering, or token/size limits considered

Tool renaming

• I am renaming tools as part of this PR (e.g. a part of a consolidation effort)
  • I have added the new tool aliases in deprecated_tool_aliases.go
• I am not renaming tools as part of this PR

Note: if you're renaming tools, you must add the tool aliases. For more information on how to do so, please refer to the official docs.

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

Docs

• Not needed
• Updated (README / docs / examples)

Note: I'm not experienced with Go, but I wanted to contribute this feature. This implementation was created with assistance from Claude Code.