feat: add review_code tool handler

TASKS.md

@@ -342,6 +342,21 @@ Create `src/tools/review-code.js` and `test/tools/review-code.test.js`.
 - OpenAI errors pass through `String(err)` unchanged (no wrapping/reformatting).
 - Mirror 4.1 and 4.2 structure: ~28 orchestration-only tests covering the same test categories.
 
+Status: ✅ Complete
+
+### Task 4.4 - debug_issue tool handler (NEXT)
+
+Create `src/tools/debug-issue.js` and `test/tools/debug-issue.test.js`.
+
+**Requirements:**
+- Export `handleDebugIssue(input, deps)` as standalone dependency-injected function.
+- Execution order: validateToolInput → loadConfig → checkContextBudget → buildDebugIssuePrompt → createOpenAIClient → sendOpenAIResponse.
+- Inject only 3 external deps: `loadConfig`, `createOpenAIClient`, `sendOpenAIResponse`. Internal utilities imported directly.
+- If budget check fails (`ok: false`), immediately return that result — do not call buildDebugIssuePrompt or create client.
+- All paths return structured `{ ok, answer|error, warnings }` — never throws to caller.
+- OpenAI errors pass through `String(err)` unchanged (no wrapping/reformatting).
+- Mirror 4.1/4.2/4.3 structure: ~28 orchestration-only tests covering the same test categories.
+
 Status: ⬜ Pending
 
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