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/smart-file-read/search.ts

@@ -13,6 +13,7 @@
 import { readFile, readdir, stat } from "node:fs/promises";
 import { join, relative } from "node:path";
 import { parseFilesBatch, formatFoldedView, loadUserGrammars, type FoldedFile } from "./parser.js";
+import { logger } from "../../utils/logger.js";
 
 const CODE_EXTENSIONS = new Set([
   ".js", ".jsx", ".ts", ".tsx", ".mjs", ".cjs",
@@ -78,7 +79,8 @@ async function* walkDir(dir: string, rootDir: string, maxDepth: number = 20, ext
   let entries;
   try {
     entries = await readdir(dir, { withFileTypes: true });
-  } catch {
+  } catch (error) {
+    logger.debug('WORKER', `walkDir: failed to read directory ${dir}`, undefined, error instanceof Error ? error : undefined);
     return; // permission denied, etc.
   }
 
@@ -114,7 +116,8 @@ async function safeReadFile(filePath: string): Promise<string | null> {
     if (content.slice(0, 1000).includes("\0")) return null;
 
     return content;
-  } catch {
+  } catch (error) {
+    logger.debug('WORKER', `safeReadFile: failed to read ${filePath}`, undefined, error instanceof Error ? error : undefined);
     return null;
   }
 }