Add documentation for new git history limiting configuration

[vim-zz]

✨ PR Description

Purpose: Add documentation for git history limiting configuration that allows restricting code expertise analysis to commits after a specific date.

Main changes:

• Added config.git_history_since parameter documentation with table entry in cm-file.md
• Created detailed usage guide with examples for the new configuration option
• Added cross-reference tips in relevant sections about code experts functionality

Generated by LinearB AI and added by gitStream.
_{AI-generated content may contain inaccuracies. Please verify before using. We'd love your feedback! 🚀}

[orca-security-us]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[gitstream-cm]

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[gitstream-cm]

✨ PR Review

The PR adds comprehensive documentation for a new git history limiting configuration. The documentation is well-structured and provides clear examples, but there's a significant discrepancy between the ticket requirements and the implemented approach.

1 issues detected:

🎯 Scope - The implementation approach doesn't align with the ticket requirements which specified individual function arguments rather than global configuration.

Details: The ticket specified adding individual 'since' arguments to specific functions (explain-code-experts action, codeExperts filter, rankByGitBlame filter), but the documentation describes a global 'config.git_history_since' configuration approach instead. This represents a fundamental architectural difference from the requested implementation.
File: docs/cm-file.md

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