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, 40 insertions, 0 deletions

diff --git a/upstreams/playwright-py/baseline/examples/element_discovery.py b/upstreams/playwright-py/baseline/examples/element_discovery.py
new file mode 100644
index 0000000..917ba72
--- /dev/null
+++ b/upstreams/playwright-py/baseline/examples/element_discovery.py
@@ -0,0 +1,40 @@
+from playwright.sync_api import sync_playwright
+
+# Example: Discovering buttons and other elements on a page
+
+with sync_playwright() as p:
+    browser = p.chromium.launch(headless=True)
+    page = browser.new_page()
+
+    # Navigate to page and wait for it to fully load
+    page.goto('http://localhost:5173')
+    page.wait_for_load_state('networkidle')
+
+    # Discover all buttons on the page
+    buttons = page.locator('button').all()
+    print(f"Found {len(buttons)} buttons:")
+    for i, button in enumerate(buttons):
+        text = button.inner_text() if button.is_visible() else "[hidden]"
+        print(f"  [{i}] {text}")
+
+    # Discover links
+    links = page.locator('a[href]').all()
+    print(f"\nFound {len(links)} links:")
+    for link in links[:5]:  # Show first 5
+        text = link.inner_text().strip()
+        href = link.get_attribute('href')
+        print(f"  - {text} -> {href}")
+
+    # Discover input fields
+    inputs = page.locator('input, textarea, select').all()
+    print(f"\nFound {len(inputs)} input fields:")
+    for input_elem in inputs:
+        name = input_elem.get_attribute('name') or input_elem.get_attribute('id') or "[unnamed]"
+        input_type = input_elem.get_attribute('type') or 'text'
+        print(f"  - {name} ({input_type})")
+
+    # Take screenshot for visual reference
+    page.screenshot(path='/tmp/page_discovery.png', full_page=True)
+    print("\nScreenshot saved to /tmp/page_discovery.png")
+
+    browser.close()
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