feat(cleanup): default idle-shutdown + keep — stop leaving scratch tabs/groups behind

Agents finish a task and just stop (never calling `close`), so daemons used to
run forever, leaving their per-session scratch tabs + tab group in the user's
Chrome. Two cases now handled:

- Default idle timeout (10 min; AGENT_BROWSER_IDLE_TIMEOUT_MS overrides, 0
  disables). On idle the daemon close()s the tabs IT created → the empty tab
  group is auto-removed by Chrome. Timer resets on every command, so active
  sessions are untouched. Adopted user tabs are never owned, so never closed.
- `keep` — leave the ACTIVE tab for the user: unown it (exempt from
  close/idle) + ask the extension to ungroup it (ABExt.ungroupTab → 0.4.12) so
  it becomes a normal tab. Scratch gets cleaned, deliverable tabs stay.

Also fix two clippy violations in the concurrently-landed #47 viewport code
(manual char comparison + iter().any→contains) that were failing main's CI.

ext 0.4.12: handle ABExt.ungroupTab (chrome.tabs.ungroup). 870 tests pass.

cli/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "chrome-use"
-version = "1.5.24"
+version = "1.5.25"
 edition = "2021"
 description = "Fast browser automation CLI for AI agents"
 license = "Apache-2.0"