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/context/ObservationCompiler.ts

@@ -207,53 +207,59 @@ function cwdToDashed(cwd: string): string {
   return cwd.replace(/\//g, '-');
 }
 
+/**
+ * Find the last assistant message text from parsed transcript lines.
+ */
+function parseAssistantTextFromLine(line: string): string | null {
+  if (!line.includes('"type":"assistant"')) return null;
+
+  const entry = JSON.parse(line);
+  if (entry.type === 'assistant' && entry.message?.content && Array.isArray(entry.message.content)) {
+    let text = '';
+    for (const block of entry.message.content) {
+      if (block.type === 'text') text += block.text;
+    }
+    text = text.replace(SYSTEM_REMINDER_REGEX, '').trim();
+    if (text) return text;
+  }
+  return null;
+}
+
+function findLastAssistantMessage(lines: string[]): string {
+  for (let i = lines.length - 1; i >= 0; i--) {
+    try {
+      const result = parseAssistantTextFromLine(lines[i]);
+      if (result) return result;
+    } catch (parseError) {
+      if (parseError instanceof Error) {
+        logger.debug('WORKER', 'Skipping malformed transcript line', { lineIndex: i }, parseError);
+      } else {
+        logger.debug('WORKER', 'Skipping malformed transcript line', { lineIndex: i, error: String(parseError) });
+      }
+      continue;
+    }
+  }
+  return '';
+}
+
 /**
  * Extract prior messages from transcript file
  */
 export function extractPriorMessages(transcriptPath: string): PriorMessages {
   try {
-    if (!existsSync(transcriptPath)) {
-      return { userMessage: '', assistantMessage: '' };
-    }
-
+    if (!existsSync(transcriptPath)) return { userMessage: '', assistantMessage: '' };
     const content = readFileSync(transcriptPath, 'utf-8').trim();
-    if (!content) {
-      return { userMessage: '', assistantMessage: '' };
-    }
+    if (!content) return { userMessage: '', assistantMessage: '' };
 
     const lines = content.split('\n').filter(line => line.trim());
-    let lastAssistantMessage = '';
-
-    for (let i = lines.length - 1; i >= 0; i--) {
-      try {
-        const line = lines[i];
-        if (!line.includes('"type":"assistant"')) {
-          continue;
-        }
-
-        const entry = JSON.parse(line);
-        if (entry.type === 'assistant' && entry.message?.content && Array.isArray(entry.message.content)) {
-          let text = '';
-          for (const block of entry.message.content) {
-            if (block.type === 'text') {
-              text += block.text;
-            }
-          }
-          text = text.replace(SYSTEM_REMINDER_REGEX, '').trim();
-          if (text) {
-            lastAssistantMessage = text;
-            break;
-          }
-        }
-      } catch (parseError) {
-        logger.debug('PARSER', 'Skipping malformed transcript line', { lineIndex: i }, parseError as Error);
-        continue;
-      }
-    }
-
+    const lastAssistantMessage = findLastAssistantMessage(lines);
     return { userMessage: '', assistantMessage: lastAssistantMessage };
   } catch (error) {
-    logger.failure('WORKER', `Failed to extract prior messages from transcript`, { transcriptPath }, error as Error);
+    if (error instanceof Error) {
+      logger.failure('WORKER', 'Failed to extract prior messages from transcript', { transcriptPath }, error);
+    } else {
+      logger.warn('WORKER', 'Failed to extract prior messages from transcript', { transcriptPath, error: String(error) });
+    }
     return { userMessage: '', assistantMessage: '' };
   }
 }