feat: add plan granularity constraint to plan-phase and creator

skills/plan-phase/SKILL.md

@@ -118,6 +118,46 @@ When the Creator receives structured feedback from a prior cycle, the proposal m
 
 CRITICAL findings cannot be deferred or disputed — they must be fixed or the proposal will be rejected again.
 
+## Task Granularity
+
+Each change item in the Creator's proposal must be a **2-5 minute task** — specific enough that the Maker can implement it without interpretation.
+
+### Requirements per Change Item
+
+Every item in the `### Changes` section must include:
+
+1. **Exact file path** — `src/auth/handler.ts`, not "the auth module"
+2. **What to change** — a code block showing the target state or transformation
+3. **How to verify** — a command or check that confirms correctness
+
+### Good Example
+
+```markdown
+1. **`src/auth/handler.ts:48`** — Add input length validation before token processing
+   ```typescript
+   if (!token || token.trim().length === 0) {
+     throw new ValidationError('Token must not be empty');
+   }
+   ```
+   **Verify:** `npm test -- --grep "empty token"` passes
+```
+
+### Bad Example
+
+```markdown
+1. **Auth module** — Fix the validation logic
+```
+
+This is too vague. Which file? Which function? What does "fix" mean? The Maker will guess.
+
+### Granularity Check
+
+- If a single change item would take **>5 minutes**, split it into smaller items
+- If a non-trivial task has **<2 change items**, it is under-specified — the Creator missed something
+- Each item should touch **1-2 files** at most. Cross-cutting changes need separate items per file.
+
+---
+
 ## Explorer Skip Conditions
 
 Not every task needs Explorer research. Use this decision table: