Fixes#88213.
Browser tab routes now use the configured action timeout for Chrome MCP existing-session reachability checks instead of failing through the old 300ms probe. Non-Chrome-MCP profiles keep the short probe, and configured timeout values are clamped to the safe timer range.
Proof: autoreview clean; node scripts/run-vitest.mjs extensions/browser/src/browser/routes/tabs.test.ts; merge-base git diff --check; PR CI green.
Co-authored-by: Ted Li <tl2493@columbia.edu>