feat: phase 3 of AI pipeline hardening — extraction quality

Replace stateless one-shot extraction with a stateful, paced, cancellable
pipeline. Six subtasks:

- 3.1 Sentence-aware chunking with 800-char overlap (was paragraph-only
  at 4000 chars). Hard-split fallback for runaway sentences.
- 3.2 Stateful extraction: chunks 2+ receive an "already-extracted topic
  IDs" hint capped at 200 IDs, so the model reuses IDs instead of
  inventing variants like software-developer vs software-engineer.
- 3.3 Token-bucket limiter in llmRetry.js (extractionLimiter, 5 req/min).
  callLLM awaits the limiter before fetch; 429+Retry-After calls
  pauseUntil. Replaces hard setTimeout(12000) and setTimeout(15000).
- 3.4 relevance_locked column on topics — admin edits to relevance are
  sticky across re-extraction. Migration + merge respects the flag +
  unlock checkbox in KnowledgeGraph edit form.
- 3.5 Unify relation vocabulary — handbook prompt no longer mentions
  legacy "executes"; one-shot migration rewrites existing executes rows
  to executed_by with source/target swapped.
- 3.6 Cancellation — Cancel button on UploadZone wired to an
  AbortController threaded into callLLM; aborted runs persist status =
  "cancelled" rather than "failed".

Tests: 16 new unit tests for chunkText, buildKnownIdsHint, and
createLimiter. All 61 tests pass, 0 lint errors, build clean.

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

src/components/admin/KnowledgeGraph.jsx

@@ -180,10 +180,17 @@ const KnowledgeGraph = () => {
   };
 
   const saveEdit = async () => {
-    await db.upsertTopic({ ...selectedNode, ...editData });
-    const updated = topics.map(t => t.id === selectedNode.id ? { ...t, ...editData } : t);
+    // If the admin touched learning_relevance, lock it so re-extraction won't overwrite the choice.
+    // But an explicit relevance_locked in editData (the unlock checkbox) always wins.
+    const relevanceChanged =
+      editData.learning_relevance !== undefined &&
+      editData.learning_relevance !== selectedNode.learning_relevance;
+    const next = { ...editData };
+    if (relevanceChanged && next.relevance_locked === undefined) next.relevance_locked = true;
+    await db.upsertTopic({ ...selectedNode, ...next });
+    const updated = topics.map(t => t.id === selectedNode.id ? { ...t, ...next } : t);
     setTopics(updated);
-    setSelectedNode({ ...selectedNode, ...editData });
+    setSelectedNode({ ...selectedNode, ...next });
     setIsEditing(false);
   };
 
@@ -265,22 +272,11 @@ const KnowledgeGraph = () => {
           setSyncProgress(`Processing ${count} of ${filesToProcess.length}: ${file.name}...`);
           try {
             const rawContent = await getFileContent('respellion', 'employee-handbook', file.path);
+            // Pacing is handled centrally by extractionLimiter inside analyzeHandbookDelta.
             await analyzeHandbookDelta(rawContent, file.path);
             await db.updateHandbookSyncState(file.path, file.sha);
-            
-            // To respect Anthropic's 5 requests per minute rate limit on this tier, 
-            // we pause for 15 seconds before processing the next file.
-            if (count < filesToProcess.length) {
-              setSyncProgress(`Waiting 15s to avoid rate limits... (${count}/${filesToProcess.length})`);
-              await new Promise(resolve => setTimeout(resolve, 15000));
-            }
           } catch (err) {
             console.error('Failed to process file:', file.path, err);
-            // We continue processing other files even if one fails, but still wait to avoid further rate limits
-            if (count < filesToProcess.length) {
-              setSyncProgress(`Error on ${file.name}. Waiting 15s... (${count}/${filesToProcess.length})`);
-              await new Promise(resolve => setTimeout(resolve, 15000));
-            }
           }
         }
         setSyncProgress('Sync Complete! Click "Analyze & Optimize Graph" above to clean up and merge.');
@@ -369,7 +365,7 @@ ${JSON.stringify({ topics: compactTopics, relations: compactRelations })}`;
       if (actions.relevanceUpdates && Array.isArray(actions.relevanceUpdates)) {
         for (const update of actions.relevanceUpdates) {
           const topicIndex = updatedTopics.findIndex(t => t.id === update.id);
-          if (topicIndex !== -1) {
+          if (topicIndex !== -1 && !updatedTopics[topicIndex].relevance_locked) {
             updatedTopics[topicIndex] = { ...updatedTopics[topicIndex], learning_relevance: update.learning_relevance };
           }
         }
@@ -532,6 +528,17 @@ ${JSON.stringify({ topics: compactTopics, relations: compactRelations })}`;
                   <option value="peripheral">Peripheral</option>
                   <option value="exclude">Exclude</option>
                 </select>
+                {selectedNode.relevance_locked && (
+                  <label className="flex items-center gap-2 text-xs text-fg-muted mt-2 cursor-pointer">
+                    <input
+                      type="checkbox"
+                      checked={editData.relevance_locked !== false}
+                      onChange={e => setEditData({...editData, relevance_locked: e.target.checked})}
+                      className="rounded bg-bg-warm border-transparent focus:ring-0 text-teal"
+                    />
+                    Locked — re-extraction will not change this
+                  </label>
+                )}
               </div>
               <div>
                 <label className="text-xs text-fg-muted uppercase tracking-wider mb-1 block">Description</label>
@@ -554,9 +561,12 @@ ${JSON.stringify({ topics: compactTopics, relations: compactRelations })}`;
               </div>
               <div>
                 <p className="text-xs text-fg-muted uppercase tracking-wider mb-1">Type & Relevance</p>
-                <div className="flex gap-2">
+                <div className="flex gap-2 flex-wrap">
                   <span className="inline-block px-2 py-1 bg-bg-warm rounded-[var(--r-pill)] text-xs font-mono">{selectedNode.type}</span>
                   <span className="inline-block px-2 py-1 bg-bg-warm rounded-[var(--r-pill)] text-xs font-mono opacity-80">{selectedNode.learning_relevance || 'standard'}</span>
+                  {selectedNode.relevance_locked && (
+                    <span className="inline-block px-2 py-1 bg-teal/10 text-teal rounded-[var(--r-pill)] text-xs font-mono" title="Re-extraction will not change relevance for this topic.">locked</span>
+                  )}
                 </div>
               </div>
               <div>