feat: threaded mini-chat per comment for fast iteration in the sidebar

[samgob]

Partner to the status.json issue I just filed — both came out of building an agent workflow on top of this skill.

Problem

Current model is one-shot: user comments → agent edits the page in response → done. If the user wants to push back on the agent's edit ("actually wait, change X" / "what about Y") their options are:

• Submit a new comment on a different block (loses the connection to the original thread)
• Scroll back to find the original block and add another comment to it (works, but each comment is still a fresh transaction)

There's no native way to have a threaded back-and-forth where the second message is clearly a follow-up to the first.

In agent-driven workflows this matters a lot. The body of the page holds the full detail of the agent's response (tables, links, code, schemas, etc.) — that's the right place for it. But the fast iteration loop on a specific point ("yes, but smaller" / "drop the second bullet" / "what's the source") wants to live in a compact sidebar lane, not as new full-fledged comments scattered through the body.

Proposal: Google-Docs-style comment threads in the sidebar

Each comment chip in the sidebar shows:

• 1-line summary of the original comment
• Status badge (Open / Working / Resolved)
• Message count + unread dot if there are agent replies the user hasn't seen
• A reply input that POSTs to /feedback with a parent_comment_id field

Click the chip → expand the thread inline. ~5 messages visible; older messages collapse. Each message has a tiny avatar (user vs agent) + the message text. Agent messages are short ("Filed 2 rows, $31.44 total"); the full detail of what the agent did still lives in the main body, anchored to the change wrapper. The sidebar is the conversation; the body is the result.

Schema sketch (additive — preserves current behavior)

feedback/comments.json (or extend inbox.jsonl entries):

{
  "id": "c-1779895383963-ok40",
  "type": "elements",
  "comment": "Yea go ahead and spin up...",
  "elements": [...],
  "created_at": "2026-05-27T15:23:03Z",
  "messages": [
    {
      "from": "user",
      "text": "Yea go ahead and spin up...",
      "at": "2026-05-27T15:23:03Z"
    },
    {
      "from": "agent",
      "text": "Filed 2 rows, total $31.44. Details in body.",
      "at": "2026-05-27T15:32:00Z",
      "links_to_change": "ch-expenses-filed"
    },
    {
      "from": "user",
      "text": "Wait, also check row 7",
      "at": "2026-05-27T15:36:00Z"
    }
  ],
  "status": "open"
}

Existing single-shot consumers (just reading inbox.jsonl for the original comment text) keep working — the messages array is additive.

UI sketch

• Right-side comment sidebar (similar to current behavior)
• Each comment chip: 1-line summary + status badge + unread count
• Click → expand inline thread (compact)
• Reply input at the bottom of each expanded thread
• Resolved threads collapse but stay accessible (toggle to show)

Full detail of the agent's response continues to live in the main body — the sidebar is just the conversational lane.

Happy to send a PR

This one is bigger than the status.json change — touches the comment-submission flow + the sidebar UI + the schema. Suggest landing it after #status-json (smaller, lower risk). Happy to send the PR; would want to align on the schema first so any downstream consumers don't break.