fix: resolve Greptile review comments on error handling

- Remove spurious console.error in logger JSON.parse catch (expected control flow)
- Remove debug logging from hot PID cleanup loop (approved override)
- Replace unsafe `error as Error` casts with instanceof checks in ChromaSync, GeminiAgent, OpenRouterAgent
- Wrap non-Error FTS failures with new Error(String()) instead of dropping details

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/utils/logger.ts

@@ -154,11 +154,7 @@ class Logger {
       try {
         input = JSON.parse(toolInput);
       } catch (_parseError: unknown) {
-        // [ANTI-PATTERN IGNORED]: Logger cannot log its own failures, using stderr/console as last resort
-        // Input is a raw string (e.g., Bash command), use as-is
-        if (_parseError instanceof Error) {
-          console.error('[logger] JSON parse failed for tool input:', _parseError);
-        }
+        // Input is a raw string (e.g., Bash command), use as-is — JSON.parse failure is expected here
         input = toolInput;
       }
     }