state-binding

# Maintain UIKitUltra State Binding Use this LOCAL contributor skill for changes to `State`, `InnerState`, mapped/merged state behavior, and built-in fluent setters that bind UIKitUltra UI/runtime properties to State. ## Load the smallest decision-complete context 1. Assume root/architecture/skill routing already selected this skill and `STATE_SYSTEM.md`; do not re-read `AGENTS.md`/`SKILL_INDEX.md` unless that context is genuinely missing or stale. 2. Use [`STATE_SYSTEM.md`](../../architecture/STATE_SYSTEM.md) as the primary owner. 3. Load [`FLUENT_CHAIN_CONTRACT.md`](../../architecture/FLUENT_CHAIN_CONTRACT.md) when a public fluent setter is added or materially changed. 4. Add [`MUTATION_MODEL.md`](../../architecture/MUTATION_MODEL.md) only for bidirectional/re-entrant/multi-state mutation. 5. Add [`RUNTIME_MODEL.md`](../../architecture/RUNTIME_MODEL.md) only for lifecycle/deferred ownership. 6. Use [`SOURCE_MAP.md`](../../SOURCE_MAP.md) only if the affected source location/ownership is not already known. Record any architecture-budget escalation rather than bulk-loading mutation/runtime contracts by default. ## Plan checklist - Record ST8 classification for every new/materially changed fluent value setter: bindable or reviewed non-bindable rationale. - Declare direction, initial assignment policy, listener ownership, repeated-call behavior, and teardown. - Record any FC11 generic exception and plan FC12 declaration-adjacent DocC for public overloads. - For two-way synchronization, identify recursion guards and mutation ordering before implementation. ## Implementation rules - Preserve State mutation order: old value -> assign -> begin -> listeners -> end. - Implement fluent setters exactly as classified under ST8 and the current fluent contract. - Do not claim listener registration is idempotent unless explicit deduplication exists. - Keep derivation (`map`) distinct from synchronization (`merge`, two-way mapping). - Preserve `InnerState` write-through parent semantics and projected propagation. - Keep listener/token ownership explicit and teardown-safe. ## Audit Verify: - State propagation ordering assumptions are correct; - ST8 classification, initial application, listener ownership, repeat behavior, and teardown match implementation; - FC11 discoverability and FC12 per-overload DocC are satisfied where applicable; - recursion protection is sound for two-way synchronization; - fluent `Self`/reference semantics remain intact; - architecture docs are changed only when the actual binding contract changed; - unrelated source/governance remains untouched. Stop and re-plan if the work requires a new State ownership/lifecycle model rather than an implementation inside current State architecture.