Goal loop input control

Problem

An active /goal is implemented as a blocking Stop hook. While the model is running, the interactive queue normally defers slash commands until the stream becomes idle. A goal loop may never reach that idle boundary, so /goal clear and replacement /goal commands cannot take effect.

The Stop response can also aggregate the goal hook with unrelated configured hooks. Clearing a goal must not discard a blocking decision owned by another hook.

Design

During an active turn, the message queue drains /goal commands alongside plain-text steering messages. Other slash commands remain queued for normal idle processing.

The CLI executes drained goal commands through the existing slash-command processor:

Clear commands apply their side effect without producing model input.
Replacement commands replace the pending goal instruction.
When multiple goal commands are drained together, only the instruction for the final active goal is sent.
The surviving instruction keeps its position relative to plain-text steering messages.
Executed goal commands are not restored if later steering preparation is cancelled; unexecuted plain-text messages are restored.

Core samples the queue before Stop hooks and again after a blocking Stop hook returns. A blocking goal output carries its goal hook ID and keeps its continuation reason separate from ordinary hook reasons. The hook bridge also reports whether another Stop output is blocking. If the goal changes at the second boundary, core removes only the old goal continuation; it still follows an independent blocking reason. Non-blocking hook outputs do not force an extra goal iteration.

Verification

Queue tests cover active-turn goal draining and idle-boundary deferral.
CLI stream tests cover clear, replacement, batched commands, ordering, and restore behavior.
Core tests cover clear and replacement during Stop-hook evaluation, including an aggregated independent blocker.
A local tmux session exercises clear and replacement against the built interactive CLI.