fix(shopfloor): Phase D review findings — defensive cleanups + bootstrap test

Important I1: tablet_session_manager.beginSession() now calls
_removeListeners() (and clears any pending _tickHandle) defensively
at start. Prevents DOM listener leak on dev hot-reload or any path
that re-bootstraps without a clean endSession() first.

Important I2: tablet_lock._checkIdle() early-returns in session_swap
mode. The tablet_session_manager owns idle tracking there (5s poll,
calls /fp/tablet/lock_session directly). Was previously dormant by
accident because session_swap never populates the legacy techStore;
explicit guard makes the decoupling intentional.

Minor M5: session_swap unlock success now resets selectedTileUserId
before window.location.reload(), matching the legacy path''s
cleanup pattern. Cosmetic before reload kicks in.

Minor M9: New test_tiles_bootstrap_fields with 3 HttpCase tests
asserting /fp/tablet/tiles returns tablet_session_mode, kiosk_uid,
and current_uid. The OWL lock screen branches on all three — a
contract regression would silently break session_swap.

Minor M10: Added inline comment near _sessionModeCache declaration
in fp_rpc.js explaining the page-reload-invalidates-cache lifecycle.

Deferred (for future polish, NOT in this commit):
- I3 (_getSessionMode ACL gap for tech users — functionally correct,
  just suboptimal; cache fallback to ''legacy'' kicks in)
- M6 (wrapper component Hand-Off buttons no-op in session_swap)
- M7 (hardcoded idle/ceiling thresholds — server-configurable later)
- M8 (timer divergence vs activity_tracker — unify later)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_shopfloor/static/src/js/services/fp_rpc.js

@@ -26,6 +26,8 @@
 
 import { rpc as baseRpc } from "@web/core/network/rpc";
 
+// Cached once per page load. Invalidated naturally by window.location.reload()
+// after every lock/unlock (the JS bundle reinitializes, cache resets to null).
 let _sessionModeCache = null;  // 'legacy' | 'session_swap' | null (unknown)
 
 async function _getSessionMode() {

fusion_plating/fusion_plating_shopfloor/static/src/js/services/tablet_session_manager.js

@@ -31,6 +31,11 @@ export const tabletSessionManager = {
             _touchHandler: null,
 
             beginSession(sessionStartedAtMs) {
+                // Defensive: if a prior session wasn't cleanly ended, remove its
+                // listeners before installing new ones. Prevents memory leaks
+                // during dev hot-reload / unexpected re-bootstrap paths.
+                this._removeListeners();
+                if (this._tickHandle) clearInterval(this._tickHandle);
                 this.sessionStartedAt = sessionStartedAtMs || Date.now();
                 this.lastActivity = Date.now();
                 this._installListeners();

fusion_plating/fusion_plating_shopfloor/static/src/js/tablet_lock.js

@@ -130,6 +130,13 @@ export class FpTabletLock extends Component {
     }
 
     _checkIdle() {
+        // In session_swap mode, the tablet_session_manager owns the idle
+        // timer (it polls every 5s and calls /fp/tablet/lock_session
+        // directly). Skip this legacy 1s-poll path to avoid two parallel
+        // idle systems competing on the same tech session.
+        if (this.state.sessionMode === "session_swap") {
+            return;
+        }
         if (!this.techStore.currentTechId) {
             this.state.idleSecondsRemaining = null;
             return;
@@ -167,6 +174,8 @@ export class FpTabletLock extends Component {
                     // Cookie has swapped. Reload so OWL/services re-init
                     // under the new (tech) session. The session manager
                     // (Task D1) picks up on the next page load.
+                    // Match the legacy path's cleanup before reload kicks in.
+                    this.state.selectedTileUserId = null;
                     window.location.reload();
                     // Return a pending state so the caller doesn't try to
                     // navigate while we're tearing down.