fix(v3): reject accidental text-selection of UI chrome (user-select policy) (#637)

* fix(v3): reject accidental text-selection of UI chrome (user-select policy)

Dragging/double-clicking across the v3 UI marquee-highlighted buttons, labels,
the sidebar, transport, and the note-highway HUD — looks broken (reported Mac +
Windows). Default the v3 shell to user-select:none on html, then opt CONTENT
back in. Decided by a 4-lens panel (UX / a11y / dev-ops / plugin-ecosystem);
their guardrails are baked in:

- Form fields ALWAYS re-enabled (input/textarea/select/[contenteditable]) so the
  caret + IME composition never break. No `* { user-select:none }` (WebKit input
  bug 82692).
- Plugin screens (.screen[id^="plugin-"]) stay selectable BY INHERITANCE (no `*`,
  so a plugin's own non-select chrome still wins) — a plugin's copyable text
  (lyrics, chords, results), including community/out-of-tree plugins that never
  adopt the class, isn't silently locked.
- Core read-only content opts back in by CONTAINER via a hand-authored
  `.fb-selectable` (not a Tailwind utility — so runtime-installed plugins get it
  too): the whole Settings panel (paths, device names, version, diagnostics,
  About) and the now-playing song metadata. Answers the open "keep settings
  copyable?" question: yes, at the container.

Cosmetic only — never used to lock copy-worthy text (errors/IDs/paths/versions/
metadata stay selectable; WCAG 2.2 allows copy-paste as a mechanism). v3-only
(v2 unchanged; v3.css loads only on /v3); plain CSS, no Tailwind rebuild; no
desktop/Electron changes (standard OS-framed window). `.fb-selectable` is
documented in CLAUDE.md for plugin authors.

Tests: tests/js/v3_user_select_policy.test.js (html default, form-field
re-enable, plugin-screen carve without `*`, .fb-selectable, container opt-ins,
and the no-`*`-rule guardrail).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QbexxfTt8q2tAn436MqGWF

* fix(v3): address review of the user-select policy (#637)

Review (manual + Codex) of the v3 text-selection policy:

- P1 (real bug): the now-playing HUD metadata opted into `.fb-selectable` but
  its `#player-hud` parent is `pointer-events: none`, so the mouse could never
  reach the text to select it — the opt-in was inert. Add `pointer-events-auto`
  to the metadata block (verified in-browser: user-select:text + pointer-
  events:auto, while the HUD parent stays pointer-events:none).
- Coverage: the PR's a11y guardrail promised copyable text stays selectable
  "incl. in modals/toasts", but only Settings + the HUD were opted in. Blanket-
  opt the focused copyable surfaces back in by selector — `.feedBack-modal`,
  `[role="dialog"]`, `#fb-notify-stack`, `#v3-fb-toast`, `#scan-banner` — so
  errors / IDs / paths / file names in dialogs, toasts, and the scan banner stay
  copyable. These are focused panels, not dense card lists, so re-enabling
  selection there can't recreate the across-cards marquee mess.
  (Deliberately NOT opting in the library grid / dashboard / profile card lists:
  making dense card text selectable would reintroduce exactly that marquee mess
  on a drag — copy song metadata from the now-playing HUD / Settings instead.)
- Test (P3): assert the selectable rule's selectors order-independently, cover
  the new modal/toast/banner surfaces, and check the HUD block carries BOTH
  fb-selectable and pointer-events-auto (class-order independent).

Verified in a real browser (chromium): html=none, sidebar chrome=none, input=
text, Settings=text, HUD meta=text+pointer-events:auto, dialog/modal=text.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: byrongamatos <xasiklas@gmail.com>

CLAUDE.md

@@ -552,6 +552,7 @@ a local pointer + code map.
 - **Storage** — `localStorage` for all user preferences
 - **Styling** — Tailwind CSS utility classes, dark theme (`bg-dark-600`, `text-gray-300`, accent `#4080e0`, gold `#e8c040`). Tailwind is served as a **prebuilt** stylesheet (`static/tailwind.min.css`, regenerated by `bash scripts/build-tailwind.sh`), **never** the runtime Play CDN — the CDN's on-the-fly JIT rescanned the DOM on the main thread and dropped ~26% of frames with the 3D highway (feedBack-desktop#110). The committed CSS only contains classes the build scanner saw, so CI (`tailwind-fresh`) rebuilds and diffs it; run the build script and commit when you add new classes. A plugin that uses classes not guaranteed in core (notably arbitrary values like `w-[37px]`) MUST ship its own compiled stylesheet via the `styles` manifest key, built with `corePlugins.preflight = false` (utilities only — core ships the one base reset). Plugins MUST NOT load the Tailwind Play CDN or any runtime CSS JIT. See constitution Principle II.
 - **Naming** — camelCase for JS functions, kebab-case for CSS classes, snake_case for plugin IDs
+- **Text selection (v3)** — the v3 UI defaults to `user-select: none` on `html` (in `static/v3/v3.css`) so accidental drag/double-click selection of chrome never looks broken. Form fields are always re-enabled, and a **plugin's mounted screen subtree (`.screen[id^="plugin-"]`) stays selectable by default**, so a plugin's copy-worthy text (lyrics, chord names, results, diagnostics) is unaffected — *unless your plugin renders copyable content OUTSIDE its `plugin-<id>` screen* (e.g. injected into the player chrome / a HUD overlay), which inherits the non-select default. Opt such content back in with the core-served **`.fb-selectable`** class (it sets `user-select: text` on the element + descendants; works for runtime-installed plugins since it's hand-authored in core CSS, not a scanned Tailwind utility). Never use a `* { user-select: none }` rule (breaks input carets/IME), and never use `user-select: none` to "lock" text — keep errors, IDs, paths, versions, and metadata selectable. (v2 is unchanged.)
 - **Player layout** — `#player` is `display:flex; flex-direction:column; position:fixed; inset:0`. `#highway` is `flex:1`. `#player-controls` sits at the bottom. Hiding the highway collapses the layout — use `margin-top: auto` on controls if you need to hide it.
 
 ## Backend Conventions