* fix(workspaces): start pasted pull requests from their branch
Recognized pull request links now select their branch directly instead of
waiting for a separate confirmation. Ensure single-branch clones also record
the fetched branch so the new worktree can track it.
* fix(workspaces): keep pasted PR checkout target-safe
* fix(workspaces): make pasted PR resolution deterministic
* fix(workspaces): preserve explicit checkout selection
A recognized pull request selects itself only when its attachment is added. Once the user chooses a branch, later composer edits must not derive checkout state from existing attachments.
* fix(composer): ignore stale pull request lookups
A lookup may finish after the workspace target changes. Only apply its attachment and selection event when the host, working directory, client, and remote still match the target that started it.
* fix(workspaces): make checkout choices authoritative
Arm automatic pull request selection only when a new PR link is detected. An explicit picker choice cancels that pending selection, existing draft attachments never infer checkout state, and target changes suppress carried-over lookups.
* fix(workspaces): stabilize pull request auto-selection
Keep the first PR selected when one edit contains several links, and accept a completed lookup when only the transport client changed for the same host and checkout.
* fix(composer): release removed pull request lookups
Release each auto-attach invocation when its composer state is abandoned, while continuing to discard any stale response.
