docs: complete phase 3 prompt builders

TASKS.md

@@ -267,8 +267,38 @@ Create `test/prompts/architecture-review.test.js`.
 Requirements:
 - Mirror structure of ask_chatgpt, review-plan, review-code, and debug-issue tests: base composition, architecture_review-specific instructions, optional fields, expectedOutput, input validation, tool guard, full integration.
 
-Status: ⬜ Pending
+Status: ✅ Complete
+
+### Task 3.8 - Phase 3 completion summary (NEXT)
+
+**Phase 3 — Tool Inputs and Prompts** is now complete.
+
+All six prompt builders are implemented and tested:
+
+| # | Prompt Builder | File | Tests |
+|---|---|---|---|
+| 0 | `buildBasePrompt` | `src/prompts/base.js` | ✅ |
+| 1 | `buildAskChatGptPrompt` | `src/prompts/ask-chatgpt.js` | ✅ |
+| 2 | `buildReviewPlanPrompt` | `src/prompts/review-plan.js` | ✅ |
+| 3 | `buildReviewCodePrompt` | `src/prompts/review-code.js` | ✅ |
+| 4 | `buildDebugIssuePrompt` | `src/prompts/debug-issue.js` | ✅ |
+| 5 | `buildArchitectureReviewPrompt` | `src/prompts/architecture-review.js` | ✅ |
+
+**What Phase 3 established:**
+
+- Prompt composition pattern: `buildBasePrompt()` → explicit `\n\n---\n\n` separator → tool-specific section.
+- All builders share the same input shape, validation rules, and optional field handling.
+- Guard rails in every builder: Claude Code remains executor; ChatGPT is advisory only.
+- `relevantFiles` inclusion with path, language (when present), and content — omitted when absent/empty.
+- Each builder passes full integration tests covering all dimensions, response structure, optional fields, and negative guards.
+
+**What Phase 3 did NOT do:**
+
+- No MCP tool registration yet.
+- No tool handlers yet.
+- No OpenAI API calls from the builders.
+- No file loading, logging, or context budget within the builders.
 
 ---
 
-Phase 2 complete. Phase 3 in progress.
+Phase 2 complete. Phase 3 complete. Phase 4 next: Tool Handlers.