fix(planning): ensure planner agent writes implementation_plan.json

- Add explicit Write tool instructions to planner.md prompt
- Clarify that agent must use Write tool, not just describe file contents
- Fix PROMPTS_DIR path in prompts.py to correctly reference prompts/ directory
- Add checkpoint reminder in Phase 4 to verify Write tool was used
- Add critical instructions for all file creation phases (init.sh, build-progress.txt)

Fixes #38

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

auto-claude/prompts/planner.md

@@ -90,9 +90,9 @@ Find these critical sections:
 cat project_index.json
 ```
 
-**IF THIS FILE DOES NOT EXIST, YOU MUST CREATE IT.**
+**IF THIS FILE DOES NOT EXIST, YOU MUST CREATE IT USING THE WRITE TOOL.**
 
-Based on your Phase 0 investigation, create `project_index.json`:
+Based on your Phase 0 investigation, use the Write tool to create `project_index.json`:
 
 ```json
 {
@@ -130,9 +130,9 @@ This contains:
 cat context.json
 ```
 
-**IF THIS FILE DOES NOT EXIST, YOU MUST CREATE IT.**
+**IF THIS FILE DOES NOT EXIST, YOU MUST CREATE IT USING THE WRITE TOOL.**
 
-Based on your Phase 0 investigation and the spec.md, create `context.json`:
+Based on your Phase 0 investigation and the spec.md, use the Write tool to create `context.json`:
 
 ```json
 {
@@ -203,6 +203,15 @@ Minimal overhead - just subtasks, no phases.
 
 ## PHASE 3: CREATE implementation_plan.json
 
+**🚨 CRITICAL: YOU MUST USE THE WRITE TOOL TO CREATE THIS FILE 🚨**
+
+You MUST use the Write tool to save the implementation plan to `implementation_plan.json`.
+Do NOT just describe what the file should contain - you must actually call the Write tool with the complete JSON content.
+
+**Required action:** Call the Write tool with:
+- file_path: `implementation_plan.json` (in the spec directory)
+- content: The complete JSON plan structure shown below
+
 Based on the workflow type and services involved, create the implementation plan.
 
 ### Plan Structure
@@ -631,8 +640,26 @@ Include parallelism analysis, verification strategy, and QA configuration in the
 
 ---
 
+**🚨 END OF PHASE 4 CHECKPOINT 🚨**
+
+Before proceeding to PHASE 5, verify you have:
+1. ✅ Created the complete implementation_plan.json structure
+2. ✅ Used the Write tool to save it (not just described it)
+3. ✅ Added the summary section with parallelism analysis
+4. ✅ Added the verification_strategy section
+5. ✅ Added the qa_acceptance section
+
+If you have NOT used the Write tool yet, STOP and do it now!
+
+---
+
 ## PHASE 5: CREATE init.sh
 
+**🚨 CRITICAL: YOU MUST USE THE WRITE TOOL TO CREATE THIS FILE 🚨**
+
+You MUST use the Write tool to save the init.sh script.
+Do NOT just describe what the file should contain - you must actually call the Write tool.
+
 Create a setup script based on `project_index.json`:
 
 ```bash
@@ -735,6 +762,11 @@ Note: If the commit fails (e.g., nothing to commit, or in a special workspace),
 
 ## PHASE 7: CREATE build-progress.txt
 
+**🚨 CRITICAL: YOU MUST USE THE WRITE TOOL TO CREATE THIS FILE 🚨**
+
+You MUST use the Write tool to save build-progress.txt.
+Do NOT just describe what the file should contain - you must actually call the Write tool with the complete content shown below.
+
 ```
 === AUTO-BUILD PROGRESS ===
 

auto-claude/prompts_pkg/prompts.py

@@ -9,7 +9,8 @@ import json
 from pathlib import Path
 
 # Directory containing prompt files
-PROMPTS_DIR = Path(__file__).parent / "prompts"
+# prompts/ is a sibling directory of prompts_pkg/, so go up one level first
+PROMPTS_DIR = Path(__file__).parent.parent / "prompts"
 
 
 def get_planner_prompt(spec_dir: Path) -> str:
@@ -38,10 +39,15 @@ def get_planner_prompt(spec_dir: Path) -> str:
 
 Your spec file is located at: `{spec_dir}/spec.md`
 
-Store all build artifacts in this spec directory:
-- `{spec_dir}/implementation_plan.json` - Subtask-based implementation plan
-- `{spec_dir}/build-progress.txt` - Progress notes
-- `{spec_dir}/init.sh` - Environment setup script
+🚨 CRITICAL FILE CREATION INSTRUCTIONS 🚨
+
+You MUST use the Write tool to create these files in the spec directory:
+- `{spec_dir}/implementation_plan.json` - Subtask-based implementation plan (USE WRITE TOOL!)
+- `{spec_dir}/build-progress.txt` - Progress notes (USE WRITE TOOL!)
+- `{spec_dir}/init.sh` - Environment setup script (USE WRITE TOOL!)
+
+DO NOT just describe what these files should contain. You MUST actually call the Write tool
+with the file path and complete content to create them.
 
 The project root is the parent of auto-claude/. Implement code in the project root, not in the spec directory.