refactor(peer): split local library and operation UI events

Replace the `a9f9845` local-update dedup cache with explicit peer event
semantics. Local scans now emit `LocalLibraryChanged` when the library changes,
while operation mutations emit `ActiveOperationsChanged` from the mutation
path. Tauri keeps joining those facts into the existing `games-list-updated`
payload, so the frontend contract stays stable.

This removes the cache/invalidation coupling between scan emission and
operation state. The remaining forced local snapshot is explicit: accepted game
directory changes can refresh the UI for an equivalent new path without sending
a peer library delta.

Operation guard cleanup and liveness cancellation now publish the same active
operation snapshot as normal command-handler transitions. The peer CLI JSONL
events follow the same split with `local-library-changed` and
`active-operations-changed`.

Test Plan:
- `just fmt`
- `CARGO_BUILD_RUSTC_WRAPPER= just test`
- `CARGO_BUILD_RUSTC_WRAPPER= just clippy`
- `git diff --check`

Refs: CLEAN_CODE_PLAN_1.md

crates/lanspread-peer/src/lib.rs

@@ -132,9 +132,10 @@ pub enum PeerEvent {
     PeerLost(SocketAddr),
     /// The total peer count has changed.
     PeerCountUpdated(usize),
-    /// Local games have been scanned, with authoritative in-progress work.
-    LocalGamesUpdated {
-        games: Vec<Game>,
+    /// The local library contents changed after a scan.
+    LocalLibraryChanged { games: Vec<Game> },
+    /// The set of in-progress local operations changed.
+    ActiveOperationsChanged {
         active_operations: Vec<ActiveOperation>,
     },
     /// A required peer runtime component failed.
@@ -168,7 +169,7 @@ pub enum InstallOperation {
     Updating,
 }
 
-/// In-progress operation snapshot attached to local library updates.
+/// In-progress operation snapshot sent when operation state changes.
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct ActiveOperation {
     pub id: String,