[omartelo]

Closes #119.

A diff could hand the session a reference — a file, a line range — but never an instruction, so anything that actually had to change was typed out by hand while looking straight at it. This adds the missing half: read the diff, leave line comments, hand them over as one turn.

What it does

Right-clicking a selection now also offers Comment on lines 12-30…, in both review surfaces — the Review dock's working diff and a pull request's Files changed. A box opens between the lines themselves, carrying the anchor as its label; ⏎ files the note, ⇧⏎ breaks a line, Esc discards it.

Comments collect at the foot of the panel in the order the diff was read, each removable on its own, and one Send hands the batch to the session as a single prompt:

Review comments:

- frontend/src/lib/use-inject.ts:12-18 — a session-less write should say so
- frontend/src/components/diff/FileDiff.tsx:52 — name this prop onReview

Sending clears them.

Decisions

• Bracketed paste, not a raw write. Newlines are what make the block readable and also what a TUI reads as send — one per line — so the batch goes in wrapped the way xterm wraps text pasted by hand. It lands in the prompt as one paste, unsent: Enter stays the user's. Verified against a real Claude Code, which takes it as [Pasted text #1 +N lines].
• The composer is a CodeMirror block widget, plain DOM. The editor owns that node; eq() keeps the widget alive across unrelated state changes so what was typed survives, and the root is contenteditable=false with every keydown stopped there, or the note would run through CodeMirror's own input handling.
• Anchors are path:12-30 — the same form the line inject already writes. No hunk is pasted inline: the provider reads the file.
• In memory, keyed by what is under review (the checkout's path, or the pull request's URL). Comments outlive leaving the tab but not a restart: an anchor is a line number of the diff as it was rendered, and outliving a restart would mean outliving every edit made in between.
• useInject now answers whether the write landed, so a Send with no session to take it says so and keeps the comments instead of dropping them.
• Not in scope: sending a comment to GitHub instead of to the session — Review: batch line comments into one prompt for the session #119 asks for that to be decided together with the review-threads work (Pulls: read and reply to review threads #122).

Ceilings

• A comment on a PR whose branch is not the session's checkout points at the session's own copy of those lines. Open in Session is the way to line them up.
• One composer per file's diff at a time; a file with only deletions has no new-file line to anchor to, so the action is disabled there.

Test plan

• frontend/src/lib/review-comments.test.ts covers the store (per-review keying, blank text, removal, notification) and the composed payload (bullets, anchors, multi-line continuation, paste markers).
• Local gate green: biome check, tsc, 516 frontend tests, vite build, go test ./... (576), go vet, gofmt.
• The render path is node-untestable, so the whole flow was driven by hand in an isolated dev instance: select → right-click → composer between the lines → ⏎ files it → bar shows the batch → Send → the session's PTY receives [Pasted text #1 +3 lines], unsent. Esc discards without touching the batch.