[Fix] Tasks hang forever when OpenCode session creation never returns

[roomote-roomote]

Opened on behalf of Matt Rubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

Related issue

Related to #379 (mitigation / fail-closed diagnostics; does not claim to fix the underlying OpenCode instance bootstrap hang).

Why this PR exists

• A maintainer explicitly invited this PR in the linked issue or discussion
• I am a maintainer / this is internal Roomote work

What changed

Self-hosted tasks that hang forever on OpenCode's first session/create bootstrap now fail closed with diagnostics instead of staying running with zero further logs.

• Unary OpenCode HTTP requests now have hard timeouts (POST /session defaults to 90s; other unary calls 60s; health 15s), overridable via env
• Request start/success/timeout/failure is logged with method, path, label, directory, timeout, and elapsed time
• Session-create failures emit a durable opencode_session_create_failed diagnostic (workspace, MCP names, HOME, model, elapsed/timeout, error)
• Initial StartNewTask failures leave a transcript-visible error and shut down as a terminal Failed run — not a resumable TaskAborted/Canceled
• Cancel while session create is pending still forces settle/shutdown on failure; a late successful create after cancel aborts that orphan session instead of starting the turn under a stopped manager

How it was tested

• Unit coverage for createSession timeout + logging
• Harness coverage for terminal failure, cancel/create success race, and diagnostics
• HarnessManager coverage for StartNewTask commandError terminal shutdown and cancel-before-session failure race
• Pre-push gates passed

Checklist

• The PR title follows the repo convention
• This PR is small and scoped to one change
• pnpm lint and pnpm check-types pass locally
• I added tests or included a clear manual validation note above
• I removed secrets, tokens, private keys, and customer data from code, logs, and screenshots
• If this change should appear in the changelog, I ran pnpm changeset

[roomote-roomote]

No new code issues found. See task

• Session-create failures used resumable TaskAborted → fixed as terminal Failed
• Cancel + later create failure discarded → fixed force shutdown after cancel
• Cancel + later create success left live orphan session → fixed abort late session / no prompt

_{Reviewed 3d85cca}

[roomote-roomote]

Fixed the successful-create cancel race too.

If CancelTask arrives before any session id exists, we still mark the cancel. A later-successful ensureSession aborts that late session and emits taskAborted — it no longer starts the initial prompt while the manager is already stopped.

Latest: cc06e11b