release: v1.19.0.0 -> v1.20.0.0 — fix tab-ownership footgun

Patch release on top of v1.19.0.0. The shipping headline of v1.19.0.0
(/scrape + /skillify productivity loop) was broken on first run in any
session where the daemon already had a tab. Bundled
hackernews-frontpage failed identically. Every /skillify-generated
skill failed identically.

The fix narrows the tab-ownership gate from "any non-root write" to
"tabPolicy === 'own-only' only." Pair-agent isolation (the v1.6.0.0
threat model) is intact; local skill spawns get their original
behavior back.

VERSION: 1.19.0.0 -> 1.20.0.0
package.json version: synced.

CHANGELOG entry leads with the user-visible impact: the productivity
loop works again, no half-second-stalls of confused 403s. Includes
before/after metrics on the bundled reference skill and the broken-
contract pre-fix tests that hid the regression.

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "1.19.0.0",
+  "version": "1.20.0.0",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",