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>

static/v3/index.html

@@ -343,7 +343,10 @@
 
     <!-- ══ SETTINGS ═══════════════════════════════════════════════════════ -->
     <div id="settings" class="screen">
-        <div class="fb-settings">
+        <!-- fb-selectable: Settings is read-only content (paths, device names,
+             version, diagnostics, About) the user copies — opt the whole panel
+             back in under the v3 non-select default. See static/v3/v3.css. -->
+        <div class="fb-settings fb-selectable">
             <button onclick="showScreen('home')" class="fb-settings-back">
                 <svg fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 19l-7-7 7-7"/></svg> Home
             </button>
@@ -825,7 +828,13 @@
 
         <!-- Top HUD — persistent (song info, time, Up Next) -->
         <div id="player-hud" class="absolute top-0 left-0 right-0 flex justify-between items-start px-5 py-4 pointer-events-none z-20">
-            <div class="text-sm leading-tight">
+            <!-- fb-selectable: now-playing song metadata (title / artist /
+                 arrangement / tuning) is copy-worthy content, not chrome.
+                 pointer-events-auto: the #player-hud parent is pointer-events-none
+                 (so the HUD doesn't eat clicks meant for the highway), which would
+                 also block the mouse from reaching this text to select it — opt
+                 just this block back into hit-testing. -->
+            <div class="text-sm leading-tight fb-selectable pointer-events-auto">
                 <div><span id="hud-artist" class="text-gray-300"></span> — <span id="hud-title" class="text-white font-semibold"></span></div>
                 <div id="hud-arrangement" class="text-gray-500 text-xs mt-0.5"></div>
                 <div id="hud-tuning" class="text-gray-500 text-xs mt-0.5"></div>