Start new workspaces from pasted pull requests (#2290)

* 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.

packages/app/src/i18n/resources/ja.ts

@@ -996,9 +996,6 @@ export const ja: TranslationResources = {
     refPicker: {
       startingRef: "開始Ref",
       chooseStart: "開始点を選択",
-      checkoutHint: "{{noun}} {{numberPrefix}}{{number}}をチェックアウトしますか？",
-      checkoutPr: "{{noun}} {{numberPrefix}}{{number}}をチェックアウト",
-      dismissCheckoutHint: "{{noun}} {{numberPrefix}}{{number}}のチェックアウトヒントを閉じる",
       intoBase: "{{baseRef}}に",
       searching: "検索中...",
       noMatchingRefs: "一致するRefがありません。",