docs(skill): clarify work item skill triggers

shared/skills/planning/work-item-definition/SKILL.md

@@ -1,12 +1,19 @@
 ---
 name: work-item-definition
-description: Turn an unclear request into a bounded technical work item.
+description: Use when a request is too vague to scope, estimate, or verify. Define the objective, scope, acceptance criteria, assumptions, dependencies, and only material open questions; do not implement it.
 ---
 
 # Work Item Definition
 
-Use when requirements, scope, or acceptance criteria are incomplete.
+Use when a request lacks enough detail to estimate or verify the intended technical outcome.
 
-Clarify the objective, boundaries, assumptions, acceptance criteria, and open questions.
+## Workflow
 
-Do not invent business requirements.
+1. State the user or system outcome in concrete terms.
+2. Define what is in scope and what is explicitly out of scope based on the request and current behavior.
+3. Write observable acceptance criteria, including relevant failure or edge cases.
+4. Record constraints, dependencies, compatibility requirements, and assumptions separately.
+5. Ask only questions whose answers would materially change behavior, contracts, permissions, or acceptance. Choose safe reversible defaults for minor implementation details.
+6. Identify unresolved risks and a proportionate verification approach.
+
+Return a bounded work item with objective, scope, criteria, assumptions, dependencies, and open questions. Do not invent business rules or start implementation unless asked.