feat(plan): add bite-sized work item decomposition to ce:plan

[mvanhorn]

Problem

/ce:plan produces great plans, but they lack structured work items. When /ce:work receives a plan, it ad-hoc decomposes it into tasks at runtime (Phase 1 Step 3: "Use TodoWrite to break plan into actionable tasks"). This decomposition:

• Happens without the planning context
• Produces coarse-grained tasks
• Misses exact file paths
• Lacks verification commands

Superpowers (42K stars) shows that bite-sized task decomposition is the #1 feature users want in planning workflows. Their plans produce 2-5 minute steps with exact paths, complete code, run commands, and expected output.

Solution

Add a Phase 5.5: Work Item Decomposition to ce:plan that generates structured work items for MORE and A LOT detail levels. Each work item includes:

• Exact file paths (create/modify/test)
• Complete code snippets in fenced code blocks
• Verification commands with expected output
• Commit boundaries with conventional messages
• TDD-first structure when applicable

Example Work Item

### Task 1: User Authentication Service

**Files:**
- Create: `app/services/auth_service.rb`
- Test: `test/services/auth_service_test.rb`

- [ ] **Step 1: Write failing test**
  [complete test code]

- [ ] **Step 2: Verify test fails**
  Run: `bin/rails test test/services/auth_service_test.rb`
  Expected: FAIL

- [ ] **Step 3: Implement**
  [complete implementation code]

- [ ] **Step 4: Verify test passes**
  Run: `bin/rails test test/services/auth_service_test.rb`
  Expected: PASS

- [ ] **Step 5: Commit**
  `git add app/services/auth_service.rb test/services/auth_service_test.rb && git commit -m "feat(auth): add authentication service"`

Implementation

Single file change to commands/ce/plan.md (~120 lines):

1. New Phase 5.5 with decomposition rules and file mapping
2. ## Work Items section added to MORE template (3-8 tasks)
3. ## Work Items section added to A LOT template (5-15 tasks, grouped by phase)
4. MINIMAL template unchanged

No changes to ce:work needed - the structured format is valid markdown that ce:work already parses.

References

• Plan with files #146 "Plan with files" - directly related
• Superpowers writing-plans skill - competitive reference
• compound engineering philosophy - 80% planning, 20% execution

I'm willing to implement this. Happy to adjust based on feedback.