fix(connect): stable per-tab relay session id — re-attach auto-recovers (#17)

When a tab's chrome.debugger session was torn down and re-established
(cross-process navigation, MV3 service-worker restart wiping the in-memory
maps, DevTools stealing the debugger), the extension minted a brand-new
monotonic `cb-tab-N` for the same tab. The daemon stays bound to the old id and
the relay consumes attach/detach events without telling it to rebind, so the
session was orphaned permanently → `stale sessionId / tab is gone`, and re-open
never recovered.

Derive the session id from the STABLE Chrome tabId (`cb-tab-<tabId>`) instead.
Any re-attach of the same tab now restores the SAME session the daemon already
holds, so eval/snapshot transparently follow the new page after a navigation.
Extension 0.4.3 → 0.4.4. Adds a relay unit test for the detach→reattach-same-
session recovery contract.

extensions/ab-connect/manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "chrome-use",
-  "version": "0.4.3",
+  "version": "0.4.4",
   "description": "Let chrome-use drive your logged-in Chrome \u2014 install once, no token, no per-use confirmation.",
   "key": "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA6vQIyscGIPYPZdSpPwPL0+0gxUROyRgCpmvCSDoc8XUm4qm97VbKnD9Ijc1lV22lNWZtE78gaRjt6BeSfuMgnBymnhLKjN1gU6AI5QUU0mrJyeHdWKvrKQR5FmsM2A7Xr1ykE2SiiS8zNUS3Y/6O5l+Nva7wrVy6E4a2dkBVQkOsu+DV+nEZvhIyuDY5D5SPXqNwUTWTaglwj5mjvHz36xSwCWlPmrtJ+ED0AUyrb2z4GIOmvk4kqtBVrh/UD058klLo4CkYOnIybB5aV6WYuwarfPY4bF/dLggPem+ewLNTUNBuwrxj/A4nUv0LJTuRO8rR7f8WR9qnRCY0Ic5saQIDAQAB",
   "icons": {