fix(claude): make checkpoint slash command deterministic

Fixes the claude /aichaku:checkpoint slash command to make it deterministic
and handle empty arguments

  - Add fallback to "session-work" when no descriptive name arguments provided
  - Add strict template constraints to prevent non-deterministic additions
  - Prohibit review dates, analyst names, and generation timestamps
  - Enforce exact section structure with explicit requirements list
  - Ensure checkpoints remain historical snapshots, not living documents

Prevents creation of malformed filenames and random metadata additions that
compromise template consistency

Author: RickCogley

claude/.claude/commands/aichaku/checkpoint.md

@@ -12,38 +12,68 @@ description: Save session summary to docs/checkpoints/checkpoint-YYYY-MM-DD-{des
 ## Your task
 Create a session checkpoint documenting our work. Use the arguments "$ARGUMENTS" as the descriptive name.
 
-Create the checkpoint file at `docs/checkpoints/checkpoint-{current-date}-{descriptive-name}.md` with the following structure:
+**CRITICAL**: 
+1. If $ARGUMENTS is empty, use "session-work" as the descriptive name
+2. Follow this EXACT template structure. Do NOT add any additional fields, headers, or metadata. 
+3. Do NOT add review dates, analyst names, or generation timestamps. This is a historical snapshot, not a living document.
+
+Create the checkpoint file at `docs/checkpoints/checkpoint-{current-date}-{descriptive-name}.md` with this EXACT structure:
 
 ```markdown
 # Session Checkpoint - {current-date} - {Descriptive Name}
 
 ## Summary of Work Accomplished
-[List main tasks completed with brief descriptions]
 
-## Key Technical Decisions  
-[Document important architectural/implementation choices and rationale]
+- [Specific task 1 with concrete outcome]
+- [Specific task 2 with concrete outcome] 
+- [Specific task 3 with concrete outcome]
+
+## Key Technical Decisions
+
+- **[Decision topic]**: [What was decided and why]
+- **[Decision topic]**: [What was decided and why]
 
 ## Files Created/Modified
 
 ### Created
-- [List new files with purpose]
+- `path/to/file.ext` - [Brief purpose]
+- `path/to/file.ext` - [Brief purpose]
 
 ### Modified
-- [List changed files with type of change]
+- `path/to/file.ext` - [Type of change made]
+- `path/to/file.ext` - [Type of change made]
 
 ## Problems Solved
-[List issues resolved and their solutions]
+
+- **[Problem]**: [Solution implemented]
+- **[Problem]**: [Solution implemented]
 
 ## Lessons Learned
-[Key insights or patterns discovered]
+
+- [Specific insight or pattern discovered]
+- [Specific insight or pattern discovered]
 
 ## Next Steps
-[Potential future work or improvements]
+
+- [Specific actionable item for future work]
+- [Specific actionable item for future work]
 
 ---
+
 *Checkpoint created: {timestamp}*
 ```
 
+**REQUIREMENTS**:
+1. Use ONLY the sections shown above
+2. Replace {current-date} with actual date (YYYY-MM-DD format)
+3. Replace {Descriptive Name} with the arguments provided
+4. Replace {timestamp} with actual timestamp
+5. Fill sections with actual content from the session
+6. Use bullet points, not numbered lists
+7. Be specific and factual, not aspirational
+8. Do NOT add Executive Summary, Key Metrics, Strategic Position, or any analysis fields
+9. Do NOT add Next Review, Generated, Analyst, or similar metadata
+
 First create the docs/checkpoints directory if it doesn't exist, then create the checkpoint file with today's date and the descriptive name from the arguments.
 
 Run a "preflight" check on the created file, making sure it is formatted and linted, then git add, git commit and git push only the created checkpoint file.