feat(peer)!: cut over to authenticated catalog sharing

Replace address-only trust and pushed peer state with installation identities,
SPKI-pinned QUIC, candidate-only discovery, and bounded responder-owned
protocol-8 pulls. The runtime now owns each network generation and all admitted
work through shutdown.

Add exact bundled content identities, reproducible manifest publishing,
capability-confined downloads, streaming BLAKE3 verification, quarantine and
retry, and crash-recoverable download and install transactions. Ship generated
fixture catalogs and fail closed when production manifests are absent.

The Tauri backend exposes durable sharing policy, redacted identity state, and
attempt-keyed transfer snapshots. Frontend consumption follows in the next
commit. Repository-wide test certificates and protocol-7 paths are removed.

BREAKING CHANGE: peers must use protocol 8 and exact catalog content artifacts;
protocol-7 frames and shared-certificate identities are no longer accepted.

Test Plan:
- `just test` -- passed on the completed stack (708 workspace tests)
- `just clippy` -- passed on the completed stack
- `just build` -- passed with fixture catalogs on the completed stack
- `just catalog-check-production` -- failed closed because the external
  production manifest corpus is absent
- `git diff --cached --check` -- passed

crates/lanspread-proto/tests/stream_install_frame.rs

@@ -1,4 +1,5 @@
 use bytes::Bytes;
+use lanspread_db::content_manifest::CanonicalCatalogPath;
 use lanspread_proto::{Message, StreamInstallFrame};
 
 #[test]
@@ -19,7 +20,8 @@ fn file_chunks_encode_raw_bytes() {
 #[test]
 fn control_frames_are_tagged_json() {
     let frame = StreamInstallFrame::FileBegin {
-        relative_path: "bin/game.exe".to_string(),
+        relative_path: CanonicalCatalogPath::new("bin/game.exe")
+            .expect("test path should be canonical"),
         size: 42,
         crc32: 0x38B4_88A7,
     };