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.

musicfs/dist/PKGBUILD

@@ -0,0 +1,23 @@
+pkgname=musicfs
+pkgver=0.1.0
+pkgrel=1
+pkgdesc="Metadata-Organized Music Filesystem"
+arch=('x86_64')
+url="https://github.com/yourusername/musicfs"
+license=('MIT')
+depends=('fuse3')
+makedepends=('rust' 'cargo')
+source=("$pkgname-$pkgver.tar.gz")
+sha256sums=('SKIP')
+
+build() {
+    cd "$srcdir/$pkgname-$pkgver"
+    cargo build --release --locked
+}
+
+package() {
+    cd "$srcdir/$pkgname-$pkgver"
+    install -Dm755 "target/release/musicfs" "$pkgdir/usr/bin/musicfs"
+    install -Dm644 "dist/musicfs.service" "$pkgdir/usr/lib/systemd/system/musicfs.service"
+    install -Dm644 "config.example.toml" "$pkgdir/etc/musicfs/config.example.toml"
+}

musicfs/dist/musicfs.service

@@ -0,0 +1,21 @@
+[Unit]
+Description=MusicFS - Metadata-Organized Music Filesystem
+After=network.target
+
+[Service]
+Type=notify
+ExecStart=/usr/bin/musicfs mount --config /etc/musicfs/config.toml /mnt/music
+ExecStop=/usr/bin/musicfs shutdown
+Restart=on-failure
+RestartSec=5
+User=musicfs
+Group=musicfs
+
+NoNewPrivileges=true
+ProtectSystem=strict
+ProtectHome=read-only
+ReadWritePaths=/var/cache/musicfs /mnt/music
+PrivateTmp=true
+
+[Install]
+WantedBy=multi-user.target

musicfs/dist/musicfs.spec

@@ -0,0 +1,39 @@
+Name:           musicfs
+Version:        0.1.0
+Release:        1%{?dist}
+Summary:        Metadata-Organized Music Filesystem
+
+License:        MIT
+URL:            https://github.com/yourusername/musicfs
+Source0:        %{name}-%{version}.tar.gz
+
+BuildRequires:  rust >= 1.70
+BuildRequires:  cargo
+BuildRequires:  fuse3-devel
+
+Requires:       fuse3
+
+%description
+MusicFS is a virtual FUSE filesystem that organizes music files by metadata.
+
+%prep
+%autosetup
+
+%build
+cargo build --release --locked
+
+%install
+install -Dm755 target/release/musicfs %{buildroot}%{_bindir}/musicfs
+install -Dm644 dist/musicfs.service %{buildroot}%{_unitdir}/musicfs.service
+install -Dm644 config.example.toml %{buildroot}%{_sysconfdir}/musicfs/config.example.toml
+
+%files
+%license LICENSE
+%doc README.md
+%{_bindir}/musicfs
+%{_unitdir}/musicfs.service
+%config(noreplace) %{_sysconfdir}/musicfs/config.example.toml
+
+%changelog
+* Mon Jan 01 2024 MusicFS Team <team@example.com> - 0.1.0-1
+- Initial package