feat: natural language review rules (#12) and optional skip deletion-only (#29)

[haasonsaas]

Summary

• Natural language custom review rules #12 Natural language review rules: review_rules_prose (YAML list) in config; prose rules section in review guidance.
• File triage: classify files before expensive review #29 Optional skip deletion-only: triage_skip_deletion_only config; TriageOptions + SkipDeletionOnly; pipeline uses options in prepare_diff_analysis.

Test plan

• cargo test (includes new config + guidance + triage tests)
• cargo clippy --all-targets
• Manual: run review with review_rules_prose and triage_skip_deletion_only: true in config.

Made with Cursor

[cursor]

PR Summary

Medium Risk
Moderate risk because it changes review prompting and triage skip behavior, which can alter what gets sent to the LLM and potentially skip reviews for deletion-only diffs when enabled.

Overview
Adds configurable natural-language review rules via review_rules_prose, and injects them into the generated review guidance as a bullet list.

Introduces an optional triage_skip_deletion_only config flag that, when enabled, classifies deletion-only diffs as SkipDeletionOnly and skips expensive LLM review; triage is refactored to accept TriageOptions and the prepare pipeline now passes this config through. Includes new unit tests and updates the roadmap shipped section.

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