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

CLEAN_CODE_PLAN_1.md

@@ -0,0 +1,70 @@
+# Clean Code Plan 1: Split Local Library and Operation UI Signals
+
+## Goal
+
+Replace the `a9f9845` local-update dedup cache with explicit event semantics.
+The peer runtime should report local library changes and active operation
+changes as separate facts, while the Tauri layer keeps joining those facts into
+the existing `games-list-updated` payload for the frontend.
+
+## Architectural Picture
+
+The current overloaded shape makes `LocalGamesUpdated` carry two independent
+signals:
+
+- local library contents, whose source of truth is `LocalLibraryState` and
+  `LocalLibraryState::update_from_scan`;
+- active operation status, whose source of truth is `Ctx::active_operations`.
+
+The clean boundary is:
+
+- peer scanning emits a local-library event when the scanned library state
+  changes, with an explicit force policy for accepted path changes where the UI
+  needs a fresh snapshot but peers do not need a delta;
+- operation-state mutation emits an operation snapshot when the mutation
+  happens;
+- Tauri owns UI joining: it stores the latest catalog/local games and latest
+  operation snapshot, then emits `games-list-updated` for the frontend.
+
+That keeps the frontend contract stable while removing the cross-cutting cache
+and every manual invalidation call.
+
+## Implementation Steps
+
+1. Remove commit `a9f9845` from the local branch history before implementing
+   the replacement, so the final code is not built on the band-aid.
+2. Replace `PeerEvent::LocalGamesUpdated { games, active_operations }` with:
+   - `PeerEvent::LocalLibraryChanged { games }`;
+   - `PeerEvent::ActiveOperationsChanged { active_operations }`.
+3. Add one operation-snapshot publisher near the peer event helpers. All normal
+   operation mutations must go through helpers that mutate
+   `Ctx::active_operations` and then emit `ActiveOperationsChanged`.
+4. Make `OperationGuard` publish an operation snapshot when it performs
+   exceptional cleanup on drop, so cancellation or aborted tasks do not leave UI
+   state stale.
+5. Keep the existing scan behavior that freezes active game summaries while an
+   operation is running, but emit `LocalLibraryChanged` only when
+   `update_from_scan` returns a real delta or the scan was explicitly forced by
+   an accepted path change.
+6. Update the Tauri event loop to reconcile `ActiveOperationsChanged`
+   independently, and call `emit_games_list` after both library and operation
+   state changes.
+7. Update focused tests in peer handlers, local monitor, liveness, context guard,
+   and Tauri reconciliation to prove:
+   - unchanged settled scans do not emit local-library events;
+   - operation starts/transitions/ends emit authoritative snapshots;
+   - exceptional guard cleanup clears the operation snapshot;
+   - Tauri still emits the same `games-list-updated` UI payload.
+8. Update `CLEAN_CODE.md`, `crates/lanspread-peer/ARCHITECTURE.md`, and
+   `crates/lanspread-peer/README.md` so the docs describe the new shape rather
+   than the dedup warning.
+
+## Review Gates
+
+- No `last_local_update_key`, `LocalUpdateKey`, or invalidate helper remains.
+- No operation-state mutation that should be visible to the UI bypasses the
+  snapshot publisher.
+- The peer event names reflect domain facts, not UI implementation details.
+- Tauri remains the compatibility boundary for the frontend payload.
+- Verification runs through `just fmt`, `just test`, `just clippy`, and
+  `git diff --check`.