perf(core): make texture renderable-owner tracking O(1) on scroll path

[chiefcll]

Why

During scroll, CoreNode.update sets the IsRenderable bit on nearly every visible node every frame, so updateIsRenderable (CoreNode.ts:1840) runs per node per frame and unconditionally called texture.setRenderableOwner (Texture.ts:276). That did an indexOf over renderableOwners: any[] — O(owners) — and SubTexture.setRenderableOwner forwards to the parent atlas texture, whose owner list can hold one entry per sprite/glyph consumer. On a representative ~13.5s trace this was ~165ms of no-op array scans.

What changed

1. renderableOwners array → Set<string | number> (Texture.ts)

• setRenderableOwner rewritten with has/add/delete and early returns on no-op calls. The 0↔1 size-transition logic (renderable flag, onChangeIsRenderable, load()) is behaviorally unchanged.
• The four .length consumers move to .size: Texture.ts, SubTexture.ts, TextureMemoryManager.ts, Inspector.ts.
• Set is supported on the Chrome 38 language floor.

2. Per-node textureOwnership cache (CoreNode.ts)

• updateTextureOwnership early-returns when ownership hasn't changed, so steady-state scroll makes zero ownership calls.
• The cache is synced at every site that touches ownership without going through the helper — unloadTexture, the texture setter (per-(node, texture) reset on swap), and the direct call in CoreTextNode — so a stale true can't skip a re-registration that triggers Texture.load(). The freed/failed handlers already route through the helper, so the freed → re-add → load() reload cycle keeps working.

Tests

• New Texture.test.ts: Set semantics (double-add no-op + single transition event, remove of non-member, 1→0 fires once, re-add after release re-triggers load(), mixed string/number owners, canBeCleanedUp owner-count behavior).
• New CoreNode ownership-cache tests: the cache skip, out-of-bounds release once, texture-swap cache reset, and the freed → reload re-registration cycle.
• All 243 unit tests pass; tsc --build clean; prettier + eslint clean on changed files.

Reviewer notes

• ⚠️ Type-surface breaking change: renderableOwners is readonly any[] in the public type and is now a Set. Anything introspecting it (Inspector does; external devtools might) breaks at the type level. Ship as a minor bump with a changelog note.
• Visual regression: this change produces zero new diffs. The local suite has ~21 pre-existing failures (one stale local svg-icons-1 snapshot + ~20 tests whose snapshots exist only under chromium-ci) that reproduce identically on clean main — verified by stashing. Unrelated to this PR; tracked separately.
• Not run here: the consuming app's suite against a linked build of this renderer (that repo isn't in this session) — worth a pnpm link smoke test on the app the 165ms trace came from.

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