test(peer-cli): add large exact-transfer coverage

Add deeper peer CLI coverage for file-transfer integrity and multi-peer
chunking. The alpha fixture now carries a real renamed RAR archive larger
than 100 MB for alienswarm, which gives the chunk planner enough work to
split a single game archive across multiple peers.

Expose completed chunk source details as a peer event and have the CLI print
that event as JSONL. This keeps transfer behavior in lanspread-peer while the
CLI remains a harness that reports what the peer runtime did. The Tauri shell
logs the event at debug level so the shared PeerEvent enum stays exhaustive.

Document the new S13/S14 scenarios and record the manual run evidence,
including SHA-256 manifests and the per-peer byte split for the large archive.

Test Plan:
- just fmt
- just test
- just peer-cli-build
- just clippy
- just peer-cli-image
- unrar t -idq crates/lanspread-peer-cli/fixtures/fixture-alpha/alienswarm/alienswarm.eti
- Manual peer CLI: bravo -> deep-small-client bfbc2 download with matching SHA-256 manifests
- Manual peer CLI: alpha -> deep-stage-b alienswarm download with matching SHA-256 manifests
- Manual peer CLI: alpha + deep-stage-b -> deep-stage-c alienswarm download with chunk events from both peers and matching SHA-256 manifests

Refs: PEER_CLI_SCENARIOS.md S13 S14

crates/lanspread-peer-cli/src/main.rs

@@ -390,6 +390,22 @@ async fn update_state_from_event(shared: &SharedState, event: PeerEvent) -> (&'s
             )
         }
         PeerEvent::DownloadGameFilesBegin { id } => ("download-begin", json!({"game_id": id})),
+        PeerEvent::DownloadGameFileChunkFinished {
+            id,
+            peer_addr,
+            relative_path,
+            offset,
+            length,
+        } => (
+            "download-chunk-finished",
+            json!({
+                "game_id": id,
+                "peer_addr": peer_addr.to_string(),
+                "relative_path": relative_path,
+                "offset": offset,
+                "length": length,
+            }),
+        ),
         PeerEvent::DownloadGameFilesFinished { id } => {
             ("download-finished", json!({"game_id": id}))
         }