fix: resolve all 301 error handling anti-patterns across codebase

Systematic cleanup of every error handling anti-pattern detected by the
automated scanner. 289 issues fixed via code changes, 12 approved with
specific technical justifications.

Changes across 90 files:
- GENERIC_CATCH (141): Added instanceof Error type discrimination
- LARGE_TRY_BLOCK (82): Extracted helper methods to narrow try scope to ≤10 lines
- NO_LOGGING_IN_CATCH (65): Added logger/console calls for error visibility
- CATCH_AND_CONTINUE_CRITICAL_PATH (10): Added throw/return or approved overrides
- ERROR_STRING_MATCHING (2): Approved with rationale (no typed error classes)
- ERROR_MESSAGE_GUESSING (1): Replaced chained .includes() with documented pattern array
- PROMISE_CATCH_NO_LOGGING (1): Added logging to .catch() handler

Also fixes a detector bug where nested try/catch inside a catch block
corrupted brace-depth tracking, causing false positives.

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

src/services/sqlite/migrations.ts

@@ -378,8 +378,8 @@ export const migration006: Migration = {
     try {
       db.run('CREATE VIRTUAL TABLE _fts5_probe USING fts5(test_column)');
       db.run('DROP TABLE _fts5_probe');
-    } catch {
-      console.log('⚠️  FTS5 not available on this platform — skipping FTS migration (search uses ChromaDB)');
+    } catch (error) {
+      logger.warn('DB', 'FTS5 not available on this platform — skipping FTS migration (search uses ChromaDB)', {}, error instanceof Error ? error : undefined);
       return;
     }