feat: add debug_issue tool handler

TASKS.md

@@ -329,7 +329,7 @@ Create `src/tools/review-plan.js` and `test/tools/review-plan.test.js`.
 
 Status: ✅ Complete
 
-### Task 4.3 - review_code tool handler (NEXT)
+### Task 4.3 - review_code tool handler ✅
 
 Create `src/tools/review-code.js` and `test/tools/review-code.test.js`.
 
@@ -357,6 +357,21 @@ Create `src/tools/debug-issue.js` and `test/tools/debug-issue.test.js`.
 - 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: ✅ Complete
+
+### Task 4.5 - architecture_review tool handler
+
+Create `src/tools/architecture-review.js` and `test/tools/architecture-review.test.js`.
+
+**Requirements:**
+- Export `handleArchitectureReview(input, deps)` as standalone dependency-injected function.
+- Execution order: validateToolInput → loadConfig → checkContextBudget → buildArchitectureReviewPrompt → 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 buildArchitectureReviewPrompt 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 4.1/4.2/4.3/4.4 structure: ~28 orchestration-only tests covering the same test categories.
+
 Status: ⬜ Pending
 
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