fix(app): show the main checkout's branch for Local in new sessions - #62061

Summary

A new session opened from a worktree session keeps that worktree as its directory. With Local selected, the branch label read that worktree, while submitting started the session in the main checkout. Local now reads the main checkout's branch, and the label and submit use the same directory, so they can't disagree again.

Fixes #55327

This supersedes #55787, which fixes the same label but conflicts with dev and expects the old New worktree behavior that dev has since changed. Thanks @udayasree25 for the earlier fix.

Changes

• new-session/workspace/controller.ts: Local and New worktree take their branch from the main checkout, and Local's branch is refreshed when it isn't the draft's own directory.
• new-session/composer-adapter.ts: submitting uses that same directory instead of working it out separately.
• E2E keeper case in e2e/regression/new-session.spec.ts: a draft opened in a worktree shows the main checkout's branch beside Local and submits there. It fails on dev.

Checks

• bun typecheck (packages/app): passes
• bun test ./src/new-session (packages/app): 75 pass
• bun run lint:changed origin/dev: 0 problems
• e2e/regression/new-session.spec.ts (built): 38 of 39 pass. The one failure, "the title and message stay stable through worktree creation", fails the same way on dev without this change.

Before / after

Draft opened in .worktrees/quiet-river (branch worktree-branch), main checkout on checkout-branch, Local selected.

Before:

After:

Visual

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  <text x="42" y="40" fill="currentColor" stroke="none" font-size="11" text-anchor="middle" font-family="sans-serif">Local</text>
  <path d="M96 24H228" stroke-opacity=".9"/>
  <path d="M128 24C148 24 148 52 168 52H228" stroke-opacity=".3"/>
  <circle cx="200" cy="24" r="5" fill="currentColor" stroke="none">
    <animate attributeName="cy" values="52;52;24;24" keyTimes="0;.35;.6;1" dur="3s" repeatCount="indefinite"/>
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  </circle>
  <path d="M72 36H90" stroke-opacity=".5" stroke-dasharray="3 3"/>
</svg>

Added by the opencode bot (AI-generated).

Related: #51992