fix(agent-pane): scope agent-run Show more to its chat (stacked on #28634)

Draft
TE
5d ago
+56-4

Fix for the independent UX-04 / MODE-06 review of #28634

Stacked on #28634 (base lane/orch-agent-pane-hunt2 at 8de2d9a420735128268066946dd3b02667b08e5e), preserving its original owner and branch. This is a small, reviewable correction for the head-pinned P2 finding; do not merge or rebase it independently of #28634.

What changed

  • AgentRunTranscriptCard wraps the existing standalone AgentRunCard in TranscriptDisclosureProvider with the real VirtualTranscript.sessionId. The prior fallback __transcript__ persisted all standalone agent-run expansions globally.
  • SubagentGroupRow passes its session ID into the wrapper and includes it in its memo equality so switching chats cannot reuse stale state.
  • Added a negative regression: chats A, B and C with the same run:call-1 ID keep independent Show more choices, including an unmount/remount. The test uses the exported wrapper that production now uses, and deliberately omits any test-only disclosure provider.

Evidence and acceptance

  • This branch has three changed files and five commits atop #28634, verified by GitHub compare: 5/4 line diff in App.tsx, 10-line wrapper, and 41-line test.
  • Code/test commit: 82af5bc3bd11981e557e1eaccc7bd2e82ea87ba0.
  • Tests have not been run in this connected GitHub session (no local checkout/fleet). This is a draft pending webviews test CI, typecheck, independent review, and optional exact-head UI capture. Suggested focused command on an authorized runner: cd webviews && bun test test/subsession-disclosure.test.tsx.
  • Acceptance: A expanded → B collapsed on same run call ID → B expanded → A stays expanded across virtualization → new chat C starts collapsed; existing ordinary sub-session disclosure tests remain green.
  • Performance: No perf numbers: the change adds one local React context provider per standalone run card and one cheap memo comparison; no polling, background work, measurement or new timer.

Ownership and release

Please review/land this scoped correction through #28634's existing implementation owner; target branch of this PR is the original feature lane, not feat-cmux-next. Do not merge #28634 before its separate existing red perf-description gate and other hold/CI issues are cleared or attributed. This PR requests no app/production rollout.

HQ dispatch: https://github.com/manaflow-ai/cmuxterm-hq/issues/5457#issuecomment-6536783040.