fix: preserve queued Goal steering across scheduler dispatch

[ByBrawe]

Summary

• preserve experimental /loop-goal across normal queued user steering instead of pausing or losing the Goal
• preempt only the in-flight Goal model turn, keep Goal state active/unpaused, let the foreground user turn run, then resume autonomous Goal work
• gate every autonomous maybeRunDueJobs path while steering is pending, including heartbeat/due/watchdog dispatch
• handle steering at OpenCode's pre-submit chat.message hook so abort cannot erase the queued foreground prompt
• keep Loop-owned synthetic prompt ownership alive across the ID-less chat.message phase and bind it when message.updated supplies the real message ID
• reject stale Goal lifecycle tool updates while foreground steering is pending
• add focused steering regressions and an exact real-OpenCode prompt_async QUEUED canary
• run the exact canary on Ubuntu + Windows for both the committed plugin and a freshly rebuilt single-file bundle
• run clean generated-bundle host verification before the full regression suite, then restore locked dependencies and run all regressions

Real-host regressions found and fixed

1. Scheduler heartbeat could bypass session.idle suppression and dispatch a second Goal before the queued user message.
2. Aborting after message.updated could cancel the already-queued foreground prompt, so steering never reached the provider.
3. Moving to chat.message exposed ID-less Loop-owned synthetic prompts; consuming their guard too early caused the Goal to abort its own continuation repeatedly.
4. Bundle Gate ran a second OpenCode server only after the full test suite, producing bootstrap timeouts unrelated to bundle semantics; clean host verification now runs immediately after rebuilding the artifact.

Final validation

• CI: success (Ubuntu/Windows full tests, minimum/current peer compatibility, real OpenCode host canaries)
• V2 Lifecycle Contract: success
• Single-file Bundle Gate: success on Ubuntu and Windows
• exact Linux real-host QUEUED proof: goalStarted=2, goalClosed=1, steeringStarted=1, goalStatus=active, paused=false
• source real-host QUEUED canary: Ubuntu + Windows success
• freshly rebuilt bundle real-host QUEUED canary: Ubuntu + Windows success
• generated-bundle full regression suite: Ubuntu + Windows success

Package version remains 0.5.28; no npm publish in this PR.

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