Document intentional empty catches, fix one real gap, allow == null in eqeqeq (#44)

ESLint flagged ~20 empty catch blocks and 4 loose-equality comparisons
in assets/js/. Auditing each: all ~19 remaining empty catches are
localStorage/sessionStorage access (persisted tab/theme/column-
visibility state, recent command-palette entries) or the terminal
beep's AudioContext calls — genuinely intentional best-effort UX
affordances that must silently no-op if storage is disabled/full or
audio is blocked, not oversights. One (a viewport-change listener
callback) was a real gap: swallowing an arbitrary caller-supplied
callback's exception could hide a genuine bug, so that one now logs
via console.error instead.

Documented the storage/audio convention once in a file-level comment
rather than repeating the same explanation on ~19 near-identical
one-line try/catches. All 4 flagged loose-equality comparisons turned
out to be `== null`/`!= null` checks — the one loose-equality idiom
that's deliberately safe (catches both null and undefined in one
comparison; ESLint's own eqeqeq rule has a "smart" mode specifically
for this). Converting them to strict equality would have been a
behavior change (no longer catching undefined), not a fix, so switched
.eslintrc.json's eqeqeq rule to "smart" instead — flags every other
loose comparison as before, correctly stops flagging this one safe
idiom.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Lhz7pGMaoTfL5sdYS5XiKv

assets/js/base.js

@@ -41,6 +41,16 @@
  *  32.  Drag & Drop Upload
  *  33.  Intersection Observer
  *  34.  Full Initialisation
+ *
+ * NOTE ON EMPTY CATCH BLOCKS: throughout this file, `try { ... } catch (_) {}`
+ * around localStorage/sessionStorage access (persisted tab/theme/column-
+ * visibility state, recent command-palette entries, etc.) and the terminal
+ * beep's AudioContext calls is intentional, not an oversight — these are
+ * best-effort UX affordances that must silently no-op rather than break the
+ * surrounding feature if storage is disabled/full (private browsing, quota)
+ * or audio is blocked (autoplay policy). Swallowing errors from arbitrary
+ * caller-supplied callbacks (e.g. viewport-change listeners) is handled
+ * separately with real logging, since those can hide genuine bugs.
  */
 
 (function (global) {
@@ -1398,7 +1408,7 @@
     _vpCurrent = bp;
     if (bp !== prev) {
       const evt = { bp, w, h, prev };
-      _vpListeners.forEach(cb => { try { cb(evt); } catch (_) {} });
+      _vpListeners.forEach(cb => { try { cb(evt); } catch (e) { console.error('[lt.viewport] listener threw:', e); } });
       bus.emit('viewport:change', evt);
     }
   }