Add a commentOnLineClick setting to keep line clicks from opening comment drafts

[azhadsyed]

TL;DR

Adds settings.commentOnLineClick (default true). When set to false, clicking or dragging on diff lines no longer opens a review comment draft, and the gutter comment button remains the way to start one.

Risk: Low
Change type: Additive

References

• Docs: README § Configuration — the settings documentation this PR extends

Background

Selecting text in a diff opened an empty comment draft under the line

To reproduce on main: open a diff, press the mouse inside a changed line, drag across a few characters, and release. An empty review comment draft opens under that line.

I select spans of code constantly while reading, so every selection left a stray draft to dismiss. The browser fires a click after a drag that starts and ends on one element, the diff library forwards it as a line click, and Codiff turns every line click into a draft. The text-selection guard only helps while the selection is still non-collapsed when that click fires.

With this change, a reader who prefers explicit commenting sets commentOnLineClick to false and keeps the gutter button (the comment control in the line-number gutter) as the one deliberate way to add a comment. Everyone else sees no change.

Architecture

One setting gating two callbacks, with the gutter button left as the explicit path

• I gate the behavior behind a setting instead of detecting a text drag in the line-click handler. Whether the selection is still non-collapsed when the click arrives depends on timing, so a guard there is flaky. A setting is deterministic.
• The setting gates onLineSelectionEnd too. The code view starts a line-range selection only from a pointer-down in the line-number column (startLineSelectionFromPointerDown in @pierre/diffs) and reports it through that callback, so a number-column drag also ended in a draft. onGutterUtilityClick is untouched, so the gutter button stays a working, explicit path.
• With the setting off I also pass enableLineSelection: false, so a number-column drag no longer highlights a range that then does nothing.
• The default is true, so existing users see no change.

Testing

Vitest cases for the gated callbacks and the config normalizer

• core/__tests__/ReviewCodeView-scroll.test.tsx: with commentOnLineClick={false}, a line click and a line-range selection end create no comment, the code view receives enableLineSelection: false, and a gutter button click still creates the comment at the expected line and section.
• core/__tests__/config-defaults.test.ts: the Electron reader keeps false when set and falls back to true on a missing or non-boolean value.
• vp check, vp run build, and the full vp test suite ran locally before pushing; CI is authoritative.
• By hand: set "commentOnLineClick": false in ~/.codiff/codiff.jsonc, run this branch, then drag across text in a diff line and drag in the line-number column. No draft opens in either case, and the gutter button still opens one.

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AI assistance: the code, tests, and this description were written with Claude Code (Claude Fable 5.1), directed and reviewed by the author.

[azhadsyed]

Visual evidence: before this change, selecting text inside a diff line opened an empty review comment draft under the line. Screenshot of that state to be attached here.

[cpojer]

Thank you for the PR. This is a regression. I noticed it as well when highlighting code and it is annoying. I will fix that without adding a new option.