Add Week 10 Plugin System and Week 11 Control API

Week 10 - Plugin System (FR-19):
- Plugin traits: Plugin, OriginPlugin, MetadataPlugin, FormatPlugin
- NativePluginHost with libloading for dynamic loading
- WasmPluginHost (feature-gated) with wasmtime runtime
- PluginManager coordinating both hosts with version checks
- OriginInstance::watch() with WatchHandle, WatchEvent for live updates
- FormatPlugin::synthesize_header() for metadata overlay

Week 11 - Control API & Production (FR-17, FR-18, NFR-6, NFR-10):
- gRPC server with full MusicFS service (status, cache, origins, events)
- Proto extended: MountState enum, TierStats, full StatusResponse/CacheStats
- WebhookHandler with HMAC-SHA256 signing and exponential retry
- Metrics with latency histograms (p50/p95/p99) and origin health gauges
- CLI with mount, status, cache, search, origin, events, shutdown commands
- E2E player compatibility tests (mpv, VLC, file manager)
- systemd service, PKGBUILD, RPM spec for packaging

Plans added for Weeks 10-14 covering P1 features.
All 154 tests passing.

docs/v2/plans/week-02-metadata.md

@@ -23,6 +23,21 @@ Implement audio metadata extraction using symphonia and create SQLite schema for
 
 ---
 
+## Task 0: Extend AudioMeta in `musicfs-core`
+
+Add `lyrics` and `composer` fields to `AudioMeta` struct (FR-6.4):
+
+```rust
+// In musicfs-core/src/types.rs, add to AudioMeta:
+pub struct AudioMeta {
+    // ... existing fields ...
+    pub lyrics: Option<String>,
+    pub composer: Option<String>,
+}
+```
+
+---
+
 ## Task 1: Metadata Parser (`musicfs-metadata`)
 
 ### 1.1 Create `Cargo.toml`
@@ -168,6 +183,12 @@ impl MetadataParser {
                         meta.year = value.chars().take(4).collect::<String>()
                             .parse().ok();
                     }
+                    StandardTagKey::Lyrics => {
+                        meta.lyrics = Some(value);
+                    }
+                    StandardTagKey::Composer => {
+                        meta.composer = Some(value);
+                    }
                     _ => {}
                 }
             }