Complete cache audit (bd-bc2c6191)

- Created CACHE_AUDIT.md with comprehensive findings
- Confirmed cache was already removed in commit 322ab63
- Fixed stale comment in internal/rpc/server.go
- All tests passing, MCP multi-repo working correctly
- Closed bd-bc2c6191

Amp-Thread-ID: https://ampcode.com/threads/T-c1286278-b1ff-4b8a-b090-2b3a1c38c9dd
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/server.go

@@ -3,7 +3,6 @@ package rpc
 // This file has been refactored into multiple files for better organization:
 // - server_core.go: Server struct definition and NewServer constructor
 // - server_lifecycle_conn.go: Server lifecycle (Start, Stop, WaitReady) and connection handling
-// - server_cache_storage.go: Storage caching, eviction, and memory pressure management
 // - server_routing_validation_diagnostics.go: Request routing, validation, and diagnostics
 // - server_issues_epics.go: Issue CRUD operations and epic status handling
 // - server_labels_deps_comments.go: Labels, dependencies, and comments operations