docs: add key bindings and skill references

docs/README.md

@@ -6,6 +6,7 @@ This folder keeps only the documentation needed to understand and maintain the e
 
 - `contract.md` — external behavior, result shape, and UX guarantees
 - `architecture.md` — module boundaries and invariants
+- `../skills/ask-user/SKILL.md` — optional agent-side decision-gate guidance
 
 ## Reading order
 

docs/contract.md

@@ -232,6 +232,12 @@ Validation is handled inside the tool so malformed calls produce the same struct
 
 The fallback message includes normalized pending questions and options so the caller can re-ask them manually. `details.questions` still contains normalized question metadata, while `details.answers` stays empty until a user responds.
 
+## Skill alignment (advisory)
+
+The optional skill profile at `skills/ask-user/SKILL.md` defines agent-side decision-gate guidance for when to call `ask_user`.
+
+It is advisory only. If there is any conflict, contract + tests win.
+
 ## Source of truth
 
 Behavior should be verified against: