[Fix] Web task-page sends steer the active turn instead of queueing silently

[daniel-lxs]

What problem this solves

Messages typed on the web task page while a turn was in flight were only appended to the runtime prompt queue and were never delivered until the turn ended — unlike Slack/Teams/Telegram follow-ups, which steer. Two user-facing consequences (found during the staging steering test pass, tasks 190holbb4xm2k, 11nl0xsy05oyl, 31qvhb7uek4gy on openmote):

• A mid-turn direction change silently sat in "Queued" for the whole turn; during a plan-mode run the agent asked the user structured questions while the user's steer — which answered them — sat undelivered.
• With a request_user_input question pending, the task deadlocked outright: the turn never ends, so the queued message never drains, and the queued message can only be rescued via the (hard to discover) queued-row steer control.

What changed

• sandboxSession.sendPrompt (web) → sandbox-server commands.sendPrompt → HarnessManager.sendFollowUpPrompt now pass autoSteerWhenQueued end to end, and the task-page prompt input sends with autoSteerWhenQueued: true.
• Delivery semantics now match provider follow-ups: native mid-turn injection into the active OpenCode session when possible (no abort, no interruption narration), falling back to queued-prompt cancel/replay when injection fails or a question is pending.
• The optimistic UI places running-turn sends in the transcript instead of the queued-messages surface to match the new delivery path. Explicit queue-only messages and the Enter-on-empty "steer oldest queued message" affordance are unchanged.
• Updated the stale steering paragraph in .agent-guidance/architecture/cloud-job-execution.md (it still described steering as cancel/replay only).

Validation

• vitest: new apps/worker sendPrompt procedure tests (flag forwarded / left unset), extended web send-prompt command test, updated PromptInput client tests — full src/app/(sandbox)/task/ suite green (476 tests), all worker procedure tests green.
• pnpm lint:fast and pnpm check-types:fast clean. Local pnpm knip output is unchanged from base (worktree-environment noise; CI knip is authoritative).

🤖 Generated with Claude Code

[roomote-roomote-v1]

No code issues found. See task