Feature request: bind --watch-artifact to an existing session; make auto-acknowledgment replies optional

Feature request

Two related asks for the Artifact comment-watch flow:

1. Route artifact comment events to an existing session — e.g. claude --watch-artifact <id> --session <session-id>, or an in-session command to claim the watch. Today --watch-artifact always spawns a fresh session.
2. Make the harness's instant auto-acknowledgment replies optional (e.g. --no-auto-reply), so the session holding the watch composes every reply deliberately.

Current behavior

• claude --watch-artifact <id> attaches a NEW session. On each comment event, the watch harness auto-posts an acknowledgment reply to the thread before the attached agent is even invoked (the agent then receives an artifact-auto-react notification stating the reply was already posted, with its comment id, and is instructed not to post another). The agent cannot suppress these.
• The auto-acks are contextless guesses at intent. In our first 15 minutes of use, two misread the user's comments: an answer to a question card ("When first needed") was acknowledged as a heading-rename request ("On it — I'll update that heading"), and another ack promised "I'll go ahead with the recommended change now" on a thread whose correct outcome was "defer".
• The passive route (live subscription armed on publish, notifying the publishing session) dropped repeatedly in our session (multiple "auto-reply subscription stopped" notices within hours), so it can't be relied on for comment events.

Why it matters

In a multi-agent build workflow, one orchestrator session holds the project's full conversational context (decisions, rationale, user preferences) and publishes commentable review pages. The user wants comment replies to come from THAT context, instantly. Today the choice is:

• watch attached → instant but contextless auto-acks (sometimes wrong, and indistinguishable on the page from deliberate replies — all show as "Claude · via the user"), or
• watch detached → correct-context replies, but only via polling or manual pings.

Being able to bind the watch (and its reply duty) to a chosen existing session — or at minimum suppress the auto-acks so the attached agent relays events to the orchestrator before anything is posted — would close the gap.

Related

#87961 (import/round-trip of artifact comment threads) — same underlying workflow: artifacts as durable, commentable review surfaces for agent-built projects.