feat(commands): /update-skills syncs forks with upstream via 3-way merge

Upstream releases fixes worth pulling into the forks (arch-decide, playwright-js, playwright-py) without losing our local modifications. Each fork now has a manifest at upstreams/<name>/ plus a committed baseline snapshot that is the 3-way merge base. scripts/update-skills.py classifies each file's drift and merges to stdout. The command owns per-file confirmation, per-hunk conflict prompts, and every target write.

I centralized manifests under upstreams/ instead of per-skill dotfile dirs because arch-decide is now two flat files in commands/ and can't carry one. A "files" map in its manifest handles the upstream rename of SKILL.md to arch-decide.md.

I seeded baselines from today's upstream HEADs, so pre-existing local modifications classify as local-only from here on. git merge-file signals hard errors as exit 255, which subprocess reports as positive. The guard treats anything 128 and up as an error so a binary-file failure isn't misread as a conflict.

1 files changed, 26 insertions, 0 deletions

diff --git a/upstreams/playwright-js/baseline/package.json b/upstreams/playwright-js/baseline/package.json
new file mode 100644
index 0000000..ada6c8b
--- /dev/null
+++ b/upstreams/playwright-js/baseline/package.json
@@ -0,0 +1,26 @@
+{
+  "name": "playwright-skill",
+  "version": "4.1.0",
+  "description": "General-purpose browser automation with Playwright for Claude Code with auto-detection and smart test management",
+  "author": "lackeyjb",
+  "main": "run.js",
+  "scripts": {
+    "setup": "npm install && npx playwright install chromium",
+    "install-all-browsers": "npx playwright install chromium firefox webkit"
+  },
+  "keywords": [
+    "playwright",
+    "automation",
+    "browser-testing",
+    "web-automation",
+    "claude-skill",
+    "general-purpose"
+  ],
+  "dependencies": {
+    "playwright": "^1.57.0"
+  },
+  "engines": {
+    "node": ">=14.0.0"
+  },
+  "license": "MIT"
+}