Support replying to inline agent comments and route replies back to the agent

[benvinegar]

Problem

Agent comments in Hunk are currently one-way annotations. You can read them, and you can add/remove/list live comments through the session CLI, but you cannot reply inline and have that reply go back to the agent as a prompt.

That makes agent-assisted review feel static instead of conversational.

Current implementation notes

Related shipped work:

• feat: add session control CLI #50 — feat: add session control CLI
• feat: add live session comment lifecycle #53 — feat: add live session comment lifecycle

Current CLI support is flat:

• hunk session comment add
• hunk session comment list
• hunk session comment rm
• hunk session comment clear

The current live comment model also appears to be flat metadata, not a thread model:

• src/mcp/types.ts → LiveComment
• src/core/liveComments.ts

There is no obvious parent/reply id, thread grouping, or transport for "send this reply back to the agent and await a response".

Potentially related foundation work:

• feat: add Hunk notify stream #77 — feat: add Hunk notify stream

That notify stream may be the right place to route agent prompts and responses.

Desired behavior

A user should be able to reply to an inline agent comment from Hunk, and that reply should be sent back to the coding agent as a prompt. The agent's answer should then come back into the Hunk session as part of the same discussion.

Acceptance criteria

• Hunk exposes a reply affordance for agent comments in the UI and/or session CLI.
• Replies preserve threading context (for example with a parent comment id or thread id).
• A reply can be routed to the connected coding agent as a prompt.
• The agent's response appears back in Hunk without losing the thread context.
• Threaded comments remain understandable in the review stream and in any CLI output.
• Add end-to-end coverage for at least one reply round-trip.

Notes

This likely needs both:

1. a thread-aware comment data model, and
2. a transport for sending reply text to the agent and receiving the response.

The notify-stream work in #77 looks like a promising building block, but the product-level workflow still needs to be defined and shipped.

[ferologics]

One flow I’m still missing: I don’t just want to reply to agent comments — I want to leave my own inline comments anywhere in the diff and have those routed back to the agent as prompts.

Imagined flow:

1. Open Hunk from the agent for the current repo/session
2. Navigate to any hunk/line
3. Press a key to add an inline comment there
4. Hunk sends that comment to the connected agent
5. The agent replies back into Hunk, ideally in the same thread

So reply support would help, but the bigger missing piece for me is native user-authored inline comments in the Hunk TUI plus a way to route them out to the agent.