chore(browser): R2 review triage on PR #308 — test rename + comment tighten

Address Copilot R2 review of 99d1182504. No functional code change.

  • test_first_call_omits_group_id_and_captures_lane → test_first_call_
    passes_wrapper_signature_and_captures_lane. The previous name was
    factually wrong since the 2.0.2 migration — the wrapper always
    passes a group_id now, just not at this layer of mocking.
    Docstring rewritten to be honest about what the test verifies.
    (Copilot R2 #5)

  • elif use_daemon: comment block extended to enumerate both daemon-
    live and daemon-dead paths. Spells out that "shared" is per-MCP-
    session (not global), so per-call isolation is preserved even in
    the fall-back path where each call spawns its own ClientSession.
    Pre-empts the next reviewer asking the same question Copilot R2 #1
    asked. (Copilot R2 #1 — comment-only; code stays as 99d1182504.)

189 passing locally. Three pre-existing/out-of-scope items from the same
review round (Copilot #2 #3 #4, Codex P2) deferred to follow-up issues —
see the consolidated PR comment for the triage rationale.

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