Three bugs in the DOM morph algorithm (web/engine.sx):
1. Empty-id keying: dom-id returns "" (not nil) for elements without an
id attribute, and "" is truthy in SX. Every id-less element was stored
under key "" in old-by-id, causing all new children to match the same
old element via the keyed branch — collapsing all children into one.
Fix: guard with (and id (not (empty? id))) in map building and matching.
2. Cleanup bug: the oi-cursor cleanup (range oi len) removed keyed elements
that were matched and moved from positions >= oi, and failed to remove
unmatched elements at positions < oi. Fix: track consumed indices in a
dict and remove all unconsumed elements regardless of position.
3. Island attr sync: morph-node delegated to morph-island-children without
first syncing the island element's own attributes (e.g. data-sx-state).
Fix: call sync-attrs before morph-island-children.
Also: pass explicit `true` to all dom-clone calls (deep clone parameter).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>