#27663 fix(harnesses): recover failed sign-in terminal launches

When opening a harness sign-in terminal fails, the Harnesses page discards the error and keeps showing “Waiting for sign-in.” The page now shows the failure, stops the waiting indicator, and keeps Sign In available to retry the same login command and folder.

Finding: “Opening that terminal is not evidence that sign-in completed.” This change handles a failed terminal launch using the existing row status and action.

Validation: static prepush gate passed; focused regression, web checks, before/after gallery captures and independent review are pending. The regression also verifies that retry does not create a chat or send a prompt. Risk is limited to the Harnesses page failure state.

Changelog

Fixed: Harness sign-in terminal failures show an error and allow retry.

Agent session: agent session

---

^{Need help on this PR? Tag @codesmith-bot with what you need.}

---

Summary by cubic

Fixes the Harnesses page so a failed sign-in terminal launch shows the error and stops the waiting indicator instead of leaving the row stuck on "Waiting for sign-in."

• Sign In stays available to retry the same login command and folder.
• Retrying does not create a chat or send a prompt.