feat(tui): let /tui/select-session target one attached TUI - #52869

Issue for this PR

Closes #53649

Also the session-switch half of #39181. The directory-scoping half of that issue isn't touched here.

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

POST /tui/select-session navigates every TUI attached to the server, because the tui.session.select handler in app.tsx only checks workspace. Directory scoping wouldn't fix that when several TUIs share one directory (for example, a session switcher that drives one of several panes in the same repo).

This adds an optional client field to the request and event, and a --client <id> flag on opencode and opencode attach. A TUI ignores a select event whose client is set to a different id. If client is left out, every TUI still navigates, so existing callers keep working.

The SDK changes come from re-running packages/sdk/js build.

How did you verify your code works?

• New test in test/server/session-select.test.ts checks that client is published with the event. The existing select tests, httpapi-sdk.test.ts, and the codemode tests pass.
• Manual check: started a server and attached two TUIs to the same session with --client a and --client b. Selecting with client: "b" moved only b. Selecting without client moved both.

Screenshots / recordings

Two TUIs attached to one server, --client a on the left and --client b on the right. Selecting with "client":"b" moves only the right one. Selecting without client moves both, as before. (mp4)

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR