fix(sdk,core): css tokenizer, override-set replay, setattribute safety, persist errors (#1350)

* fix(sdk,core): css tokenizer, override-set replay, setattribute safety, persist errors

* test(sdk,ci): smoke test + explicit sdk-tests CI gate

Smoke test covers the full public surface:
  openComposition → setStyle/setText/dispatch(moveElement) → serialize
  applyPatches + ORIGIN_APPLY_PATCHES tagging
  batch() coalescing + transactional rollback on throw
  undo/redo round-trip
  persist adapter write + persist:error surfacing
  T3 embedded mode: override-set apply on open + getOverrides round-trip

Adds sdk-tests CI job so SDK coverage is explicitly named and required —
prevents a repeat of the demo-next vitest-never-ran incident.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(sdk): export adapter types, awaitable flush(), never-coalesce mode

- Export PersistAdapter, PreviewAdapter, PersistVersionEntry from package
  root — callers can now write typed fakes without reaching into internals
- Add flush(): Promise<void> to Composition interface + CompositionImpl —
  app-close handlers can await a clean drain of the persist queue
- coalesceMs <= 0 disables coalescing entirely in createHistory — enables
  deterministic test scenarios without per-entry timestamp manipulation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test(sdk): p2 edge cases — setText no-text-node, override-remove non-existent, flush in smoke

- setText on element with no prior text node (firstTextIdx=-1 path)
- applyOverrideSet null removal on non-existent prop is a no-op (no throw)
- smoke persist test uses comp.flush() instead of setTimeout
- can() JSDoc clarifies Phase 3b false-return is intentional feature-detection

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* ci: trigger regression suite

* fix(ci): add packages/sdk/package.json to Dockerfile.test workspace copy

bun install --frozen-lockfile fails in the regression Docker build because
the lockfile references the sdk workspace member but its package.json was
not copied into the image before the install step.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/sdk/src/session.test.ts

@@ -89,11 +89,22 @@ describe("override-set replay on open", () => {
     expect(comp.serialize()).not.toContain("subtitle");
   });
 
-  it("treats property-level null as restore-base (no-op on fresh base)", async () => {
+  it("treats property-level null as a deletion marker — removes the property from the base", async () => {
+    // Null in the override-set is emitted only from patchRemove (explicit deletion).
+    // On replay against a base that has the property set, it must be removed.
     const comp = await openComposition(BASE_HTML, {
       overrides: { "hf-title.style.color": null },
     });
-    expect(comp.getElement("hf-title")?.inlineStyles["color"]).toBe("#fff");
+    expect(comp.getElement("hf-title")?.inlineStyles["color"]).toBeUndefined();
+  });
+
+  it("null removal override on non-existent property is a safe no-op", async () => {
+    // backgroundColor doesn't exist on hf-title in the base; removing it must not throw.
+    const comp = await openComposition(BASE_HTML, {
+      overrides: { "hf-title.style.backgroundColor": null },
+    });
+    expect(comp.getElement("hf-title")).not.toBeNull();
+    expect(comp.getElement("hf-title")?.inlineStyles["backgroundColor"]).toBeUndefined();
   });
 
   it("getOverrides returns the set the session was opened with", async () => {