docs(skill): clarify planning skill triggers

shared/skills/planning/implementation-planner/SKILL.md

@@ -1,12 +1,19 @@
 ---
 name: implementation-planner
-description: Create a concise plan for implementing an understood change.
+description: Use when requirements are understood but implementation needs multiple dependent steps, affected areas, risk handling, or coordinated verification. Produce a plan without making the changes.
 ---
 
 # Implementation Planner
 
-Use before implementation when a change has multiple meaningful steps.
+Use when an understood change has multiple dependent steps or meaningful coordination risk.
 
-Identify the goal, affected areas, sequence, risks, and verification.
+## Workflow
 
-Return a short actionable plan. Do not implement the change.
+1. Restate the intended outcome and acceptance conditions without expanding the request.
+2. Identify the files, components, data contracts, or workflows likely to change. Confirm the repository's existing patterns before proposing new structure.
+3. Order work by dependency. Keep steps small enough to review and verify independently where possible.
+4. Call out decisions that affect compatibility, data, permissions, or external systems. Resolve routine reversible choices using repository conventions.
+5. Pair each substantial step with the cheapest useful verification.
+6. Keep the plan concise and omit speculative scaffolding, unrelated cleanup, and work that can safely wait.
+
+Return an actionable sequence with affected areas, risks, and checks. This skill plans only; do not implement the change.