chore: calibrate CodeRabbit from recent reviews

[Microck]

what changed

recent reviews found good signal, but they also exposed repeated gaps around backup retention, StartPos ownership, reconstructed state, warm-cache budgets, GC hooks, and the stripped Celeste reference environment.

this adds narrow path instructions for those cases. the existing docs check, inherited organization config, filters, and review cadence stay unchanged.

validation

• uvx --from check-jsonschema==0.37.4 check-jsonschema --schemafile https://coderabbit.ai/integrations/schema.v2.json .coderabbit.yaml
• confirmed every new glob matches repository paths
• reviewed all commits and PRs since the previous config update, including 42 CodeRabbit findings across PRs docs: audit and align public documentation #131, fix: restore StartPos slots across rooms and restarts #132, and fix: make StartPos restores and Windows backups fail safe #135
• no game build or remote Celeste check, since this only changes review configuration

ai assistance disclosure

• agent_name: Codex
• agent_version: current Codex API agent
• model_used: model_not_exposed because the exact provider model identifier is not exposed in this session
• human_testing: config and schema review only
• contribution_summary: reviewed the commit and PR history, classified review feedback, and drafted the path-specific calibration