carry of #27663: make failed sign-in retry safe
Carries #27663: failed Harnesses sign-in terminal launches must show the failure and keep Sign In available to retry the same login command.
The original PR's exact-head review found a P2 where a health refresh could change a failed row to ready; clicking the retained Sign In action then called act(row), started a chat, and lost the login retry. This carry stores the original login command in the failed progress state and routes retries directly through the terminal opener, independent of the current health status.
Validation: git diff --check passed. Added a regression covering a failed launch followed by a health refresh to ready, asserting the retry opens the same terminal command and never calls chat.new. Fleet web test was unavailable while the broker was rate limited during preparation.
Original PR: https://github.com/manaflow-ai/cmux/pull/27663
Agent session: agent session