test: update tests left pointing at the removed browser

[arzafran]

What this does

Turns main CI green again after #403. The app was fine; three tests still expected the removed browser.

• Bonsplit package tests used the removed "New Browser" split tooltip and the reload tab action. They no longer compiled, which stopped unit-test shard 2 before it ran anything.
• test_mcp_server_e2e.py hard-coded 13 focus_ tools. There are 10 now that the three focus_browser_* tools are gone; the count now follows the expected-name set the test already checks.
• testAttachedTransferIgnoresStaleFinalizeAndNextDetachHasIndependentOwnership expected a finalized terminal to stop at closing. Closing a terminal panel tears its surface down right away, so the state is closed. The assertion was new in refactor: remove the built-in browser #403 and never ran.

Test plan

• CI green, including unit-tests shard 2 (first full run since refactor: remove the built-in browser #403).

Local: Bonsplit tests compile with swift build --build-tests. No tests run locally.