execution_loop: align overseer log/KB strings with reverted local route

Yesterday's revert (d054c0b) changed the API CALL from cloud to local
but missed the LogEntry + KB row that record what model fired. Result:
honest API call to qwen3.5:latest, dishonest log/KB rows saying
"claude-opus-4-7". That's a real audit-trail integrity issue — the
record didn't match reality.

Fixed:
- LogEntry "system" role label (line 663)
- KB row's "model" field (line 685)

Both now correctly show "qwen3.5:latest". Build + restart + smoke
10/10 green. Gateway healthy.

Side note: the only remaining "claude-opus-4-7" mentions in this file
are now in COMMENTS describing the v1 cloud route + the revert
rationale — those are documentation, not log fields. Safe to keep.

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

crates/gateway/src/execution_loop/mod.rs

@@ -660,7 +660,7 @@ impl ExecutionLoop {
 
         // Append to the transcript so the next executor turn sees it.
         self.append(LogEntry::new(
-            turn, "system", "claude-opus-4-7", "overseer_correction",
+            turn, "system", "qwen3.5:latest", "overseer_correction",
             serde_json::json!({
                 "reason": reason,
                 "correction": correction_text,
@@ -682,7 +682,7 @@ impl ExecutionLoop {
             "task_class": self.req.task_class,
             "operation": self.req.operation,
             "reason": reason,
-            "model": "claude-opus-4-7",
+            "model": "qwen3.5:latest",
             "correction": correction_text,
             "applied_at_turn": turn,
             "kb_context_used": kb,