Remove drag-to-reorder (rollback #10/#23)

[GeneralD]

Closes #102.

Stacked on #104 (revert/103-remove-wheel-scroll) to avoid conflicts in the shared files (config.rs, lib.rs, line.rs, README). Merge #104 first; GitHub then auto-retargets this PR to main. The diff below is reorder-only.

Why

Drag-to-reorder (#10, opt-in since #23) never worked in normal use: zellij does not deliver the tab-drag Hold/Release mouse events to a non-selectable default_tab_template bar, so the gesture was inert — root cause confirmed in #102. This is the same dead-end that sank wheel-scroll (#103): a mouse gesture aimed at a pinned, non-focusable bar that the host never routes there.

Keeping the feature meant carrying dead code, a dormant RunActionsAsUser permission, and an opt-in flag for something that can't fire. Removing it is cleaner than gating inert code.

What changed

• config — drop the reorder key. Parsing is total (get(key).and_then(parse).unwrap_or(DEFAULT)), so existing layouts keep loading; a leftover reorder "true" is simply ignored.
• permissions — the bar now always requests exactly two: ReadApplicationState + ChangeApplicationState. RunActionsAsUser is no longer requested. Dropping a permission is freeze-safe — zellij#4982 only freezes the bar when adding a permission not in the cached grant, never when removing one.
• drag mechanics removed — DragState, the press/Hold/Release handling, and the line::Shift / drag_steps / drop-resolution layout math (plus their unit tests).
• left click on a tab is now purely switch / focus-pane (mouse: click a minimap pane to focus it (position -> pane hit-test) #74) / close (mouse: an 'x' close button on each tab block (click hit-test) #86) / new-tab (mouse: a '+' button at the end of the tab strip to open a new tab #76) — the press no longer arms a drag.
• docs — README config example + the "Enabling reorder" permission note, and the cliff.toml release-notes permission hint, are removed.

docs/design.md keeps its original v2 D&D design notes as a historical record (internal Japanese planning doc — out of scope to rewrite here).

Note

#93 (pane drag-to-move) was planned to reuse this same DragState/Hold mechanism (per #102). That mechanism is now gone; #93 would need a fresh approach if ever revisited — but it hits the identical host limitation, so it is unlikely to be viable as a bar gesture.

Breaking change

The reorder config key is removed and the bar no longer requests RunActionsAsUser. Layouts that set reorder "true" keep working (the key is ignored) and can drop it.

Verification

• cargo build --target wasm32-wasip1 — clean
• CARGO_BUILD_TARGET=aarch64-apple-darwin cargo test --lib — 242 passed
• cargo clippy --target wasm32-wasip1 --all-features --lib (CI's command) — clean
• cargo fmt --check — clean

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c6c9ebb9-1092-4277-bd0e-8b42ca4c896e

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch revert/102-remove-inert-reorder

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[Copilot]

Pull request overview

This PR rolls back the drag-to-reorder feature by removing the reorder config/permission surface area and deleting the associated drag state + layout math. It aligns the implementation with the confirmed host limitation (no Hold/Release delivery to this non-selectable bar), leaving left-click behavior as switch/focus/close/new-tab only.

Changes:

• Removed drag-to-reorder layout math (Shift, drag_steps, drop clamping) and its unit tests.
• Removed drag state machine (DragState, Hold/Release handling, reorder planning/emission) and simplified permissions to a fixed two-permission set.
• Removed reorder configuration key and updated docs/release-notes hints accordingly.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/line.rs	Deletes drag-to-reorder hit-test/drop-resolution helpers and related tests; updates docs to reflect click-only usage.
src/lib.rs	Removes drag state + Hold/Release handling; makes permissions fixed (Read + Change only); updates tests accordingly.
src/config.rs	Drops the reorder config field/default/parsing/tests so the key becomes ignored.
README.md	Removes reorder from the config example and deletes the “Enabling reorder” permission note.
cliff.toml	Removes the release-notes hint about adding RunActionsAsUser when reorder is enabled.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.