Abort or reconfirm when automatic worktree creation fails

[AetherAI3]

Problem

prepareWorkspace promises an isolated worktree when gh is authenticated, but a failed git worktree add silently changes the execution target to the original checkout and still returns proceed: true. With --yes, no user can review that change of plan before the coding agent starts.

Reproduction (current main, b037891)

Use the injected Runner in prepareWorkspace with gh auth status successful, --is-inside-work-tree returning true, and every git worktree add returning a failure such as permission denied. Use ctx.flags.yes = true and a non-TTY PromptIO.

Observed return value after the worktree attempts fail:

{"cwd":"C:/scratch/repo","proceed":true}

The notes first say “Spinning up an isolated worktree so your branch stays untouched…” and then “working in place.” The caller receives no indication that it must stop or obtain new consent.

Relevant code: src/commands/code_support.ts in prepareWorkspace; src/core/worktree.ts in createGatedWorktree. test/repo_gate.test.ts covers successful creation and unauthenticated in-place behavior, but not failure after isolation was attempted.

Expected

A worktree failure must not begin the coding task on the original branch under the prior --yes approval. Abort with the Git error, or in an interactive session require a fresh explicit choice to work in place. Add a regression test for the failed worktree path, including --yes.

[AetherAI3]

Resolved by PR #200, merged as aad70f2 (fix commit a227524).

Verification:

• On the exact PR head, a clean Ubuntu/WSL checkout with Node 24 passed the full npm test suite: 2,830 passed, 0 failed, 11 skipped.
• On current main (41e34e7), the repo-gate suite passed 7/7, including failed worktree creation under non-TTY --yes and the command's exit code 1. The fix commit is an ancestor of current main.
• Typecheck, documentation check, production verification, four Python fixture verifiers, npm audit tests, and PyPI launcher unit tests passed locally.
• The current-main Windows full run had 2,826 passes and two unrelated timing failures (Edge composer discovery and process-tree startup); each failing test passed when rerun in isolation. Neither path was changed by PR fix(code): abort when automatic worktree creation fails #200.

GitHub's required Actions jobs did not start because the account was locked due to a billing issue; this is recorded on the PR. The repository owner authorized local verification and the merge. The coding command now stops with the Git error instead of running on the original checkout after failed automatic worktree creation.