release: sync main resolution and version gate into dev

[numnx]

Summary

Syncs current main conflict resolution back into dev before the release promotion, bumps the package version to 0.9.2, and adds a CI gate that requires future main release PRs to include a version bump.

What Changed

• Merged current main into the release promotion branch so dev receives the E2E and workflow conflict resolutions before the final main PR.
• Preserved the isolated Playwright E2E fixture helpers from dev while adding the deterministic agent preset fixture helper from main.
• Resolved E2E conflicts in the avatar scene, accessibility smoke, and sprint ledger responsive specs.
• Kept the protected-branch-safe models.dev catalogue PR workflow wording from main.
• Bumped package.json from 0.9.1 to 0.9.2.
• Added Release Version Bump to CI for pull requests targeting main; it compares package.json between the PR head and target main commit and fails unless the version increases.
• Documented the main release version gate and corrected the Playwright E2E trigger policy documentation.

Validation

pnpm run lint
git diff --check
python3 - <<'PY'
import yaml
from pathlib import Path
for path in Path(".github/workflows").glob("*.yml"):
    yaml.safe_load(path.read_text())
print("workflow yaml ok")
PY
node - "0.9.1" "0.9.2" <<'NODE'
const [, , baseVersion, headVersion] = process.argv;
const semverPattern = /^(\d+)\.(\d+)\.(\d+)(?:[-+][0-9A-Za-z.-]+)?$/;
function parseVersion(value, label) {
  const match = semverPattern.exec(value);
  if (!match) throw new Error(`${label} package.json version is not valid semver: ${value}`);
  return match.slice(1, 4).map(Number);
}
const base = parseVersion(baseVersion, "Base");
const head = parseVersion(headVersion, "Head");
const isGreater = head[0] > base[0]
  || (head[0] === base[0] && head[1] > base[1])
  || (head[0] === base[0] && head[1] === base[1] && head[2] > base[2]);
if (!isGreater) throw new Error(`Main release PRs must bump package.json version above ${baseVersion}; found ${headVersion}.`);
console.log("version comparator ok");
NODE

Risk / Rollback

Low runtime risk: this PR only syncs release branch resolution, package metadata, CI, E2E conflict resolution, and docs. Roll back by reverting this PR before creating the final main release PR.