fix: duplicate optAutoRedact ID + hardcoded log limit + add test suite

Bug 1: popup.html had duplicate id="optAutoRedact" on both the
Auto Redact toggle and Auto-redact Detected PII toggle. The second
overwrote the first, making the Auto Redact setting uncontrollable.
Fixed by giving the second toggle id="optAutoRedactDetected".

Bug 2: injector.js hardcoded activity log trim to 100, ignoring the
user's maxLogEntries setting. Now reads the setting from storage.

Added test-suite.html with 35+ tests covering storage, encryption,
sync (encryption-mandatory flows), auto-redact (built-in + custom
patterns), substitution engine, smart patterns, and auto-detect.

https://claude.ai/code/session_01KF4i7Ra7zCEDskxDBaNtcT

src/popup/popup.html

@@ -217,7 +217,7 @@
           <strong>Auto-redact detected PII</strong>
           <span class="setting-desc">Replace detected PII with placeholders on send</span>
         </div>
-        <label class="toggle"><input type="checkbox" id="optAutoRedact" checked><span class="toggle-slider"></span></label>
+        <label class="toggle"><input type="checkbox" id="optAutoRedactDetected" checked><span class="toggle-slider"></span></label>
       </div>
 
       <div class="setting-item">

src/popup/popup.js

@@ -222,7 +222,7 @@ async function initUnlockedUI() {
   // Load options tab settings
   $('#optAutoRedact').checked = settings.autoRedact !== false;
   $('#optAutoDetect').checked = settings.autoDetect !== false;
-  $('#optAutoRedact').checked = settings.autoRedactDetected !== false;
+  $('#optAutoRedactDetected').checked = settings.autoRedactDetected !== false;
   $('#optHighlights').checked = settings.showHighlights || false;
   $('#optDocPreview').checked = settings.docScanPreview !== false;
 
@@ -230,7 +230,7 @@ async function initUnlockedUI() {
   const optHandlers = [
     ['optAutoRedact', 'autoRedact'],
     ['optAutoDetect', 'autoDetect'],
-    ['optAutoRedact', 'autoRedactDetected'],
+    ['optAutoRedactDetected', 'autoRedactDetected'],
     ['optHighlights', 'showHighlights'],
     ['optDocPreview', 'docScanPreview'],
   ];