feat(dom): implement true multi-surface DOM rendering (#115)

Each surface renders as a separate <section> with accessible label and
unique DOM id. Multi-surface screens use --<surfaceName> suffixed DOM
ids for asks, actions, hints, reasons, and feedback outputs to avoid
duplicates. Single-surface screens preserve backward-compatible DOM
output (no suffix, no section wrapper).

Duplicate ask controls across surfaces share underlying state via
reactive subscriptions. Duplicate action buttons execute the same
action. Blocked reasons, aria-describedby, Enter key hints, and
feedback output are scoped per surface copy.

16 new tests cover multi-surface sectioning, id suffixing, item
scoping, shared state (text/checkbox/select), shared actions,
enabled/disabled sync, scoped blocked reasons, scoped aria-describedby,
per-surface feedback, Enter key per surface, semantic id preservation,
and cleanup.

Author: mahyarmlk

.changeset/many-experts-chew.md

@@ -0,0 +1,6 @@
+---
+"@intent-framework/dom": patch
+---
+
+renderDom now renders each surface as a separate `<section>` with accessible label and unique DOM id. Multi-surface screens use `--<surfaceName>` suffixed DOM ids to avoid duplicates. Duplicate ask controls across surfaces share underlying state; duplicate action buttons execute the same action. Single-surface screens preserve backward-compatible DOM output with no suffixing or section wrappers.
+

docs/proposals/Dom-Multi-Surface-Rendering.md

@@ -1,12 +1,12 @@
 # DOM Multi-Surface Rendering
 
-**Status:** Design Proposal  
+**Status:** Implemented (PR #115)  
 **Date:** 2026-06-26  
 **Author:** Big Pickle  
 **Lane:** `renderer/dom`  
 **Depends on:** Nothing  
 **Affected package:** `@intent-framework/dom`  
-**Changeset:** None (proposal-only)
+**Changeset:** Patch for `@intent-framework/dom`
 
 ---