fix(resolution): filter stale-target edges so watch sync survives FK violations (#455) (#463)

PR #62 plugged this FK violation at the extraction-layer insertEdges site
(empty-named nodes whose containment edges had no target), but the same
violation kept reappearing on v0.9.5 during the daemon's *watch sync* once an
agent's daemon had been running long enough. The resolution-layer insertEdges
(and the callback-synthesizer pass) wasn't guarded the same way: a per-resolver
name cache or a framework resolver's WeakMap-keyed lookup map could hand back
a Node whose row had been removed by a recent file rewrite, and the FK check
then aborted the entire resolution batch, leaving the daemon log filling with
`Watch sync failed { error: 'FOREIGN KEY constraint failed' }`.

The resolution layer now mirrors the #62 defense — one cache-aware
getNodesByIds per pass drops any edge whose source or target is no longer in
the nodes table, so the rest of the resolved batch still lands.

Regression test seeds the resolver's nameCache with a stale Node and calls
resolveAndPersist directly; verified to throw FOREIGN KEY constraint failed
without the fix and pass with it. Full suite: 984/984 pass.

Closes #455.

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

src/resolution/callback-synthesizer.ts

@@ -812,6 +812,19 @@ export function synthesizeCallbackEdges(queries: QueryBuilder, ctx: ResolutionCo
     seen.add(key);
     merged.push(e);
   }
-  if (merged.length > 0) queries.insertEdges(merged);
-  return merged.length;
+  if (merged.length > 0) {
+    // Defense-in-depth (issues #42, #455): drop edges whose source/target
+    // no longer resolves to a real node. Some channel maps cache native
+    // Node refs across a resolver lifetime (WeakMap-keyed by context), so
+    // a file rewrite between map build and synthesis can leave stale IDs
+    // here. One FK violation aborts the whole batch — better to skip the
+    // dead edges and emit the rest than lose every synthesized edge.
+    const allIds = new Set<string>();
+    for (const e of merged) { allIds.add(e.source); allIds.add(e.target); }
+    const existing = queries.getNodesByIds([...allIds]);
+    const validEdges = merged.filter((e) => existing.has(e.source) && existing.has(e.target));
+    if (validEdges.length > 0) queries.insertEdges(validEdges);
+    return validEdges.length;
+  }
+  return 0;
 }