docs: v1.3.0.0 — complete CHANGELOG + bump for post-1.2 scope additions

VERSION 1.2.0.0 → 1.3.0.0. The original 1.2 entry was written before I
added substantial new scope: the /benchmark-models skill, /ship Step 19.5
gstack-publish integration, --dry-run on gstack-model-benchmark, and the
lite E2E test coverage (4 new test files). A minor bump gives those
changes their own version line instead of silently folding them into
1.2's scope.

CHANGELOG additions under 1.3.0.0:
- /benchmark-models skill (new Added)
- /ship Step 19.5 publish check (new Added)
- gstack-model-benchmark --dry-run (new Added)
- Token ceiling 25K → 40K (moved to Changed)
- New Fixed section — codex adapter --skip-git-repo-check, --models
  dedupe, CI Dockerfile xz-utils + nodejs.org tarball
- 4 new test files documented under contributors (taste-engine,
  publish-dry-run, benchmark-cli, skill-e2e-benchmark-providers)
- Ship golden fixtures for claude/codex/factory hosts

Pre-existing 1.2 content preserved verbatim — no entries clobbered or
reordered. Sequence remains contiguous (1.3.0.0 → 1.1.3.0 → 1.1.2.0 →
1.1.1.0 → 1.1.0.0 → 1.0.0.0 → 0.19.0.0 → ...).

package.json and VERSION both at 1.3.0.0. No drift.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "1.2.0.0",
+  "version": "1.3.0.0",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",