fix(model-settings-menu): make the level being edited readable

[Harry19081]

Problem

Four defects in the model pill's settings surface, all of the same kind — the UI
did not report the state it was editing.

1. No feedback while dragging the effort slider. EffortSlider deliberately
   keeps a gesture local (// Keep rapid input local; persist only the completed gesture) and fires onChange on release. The compact panel passes
   showLabel={false}, so during a drag the fill moved but nothing anywhere —
   panel or pill — said which level the thumb had reached.
2. The level was hard to read while editing it. The pill renders it in
   text-text-3 so the model name leads. That is right at rest and wrong while
   the panel that edits it is open.
3. Submenu rows overflowed their row box. The Effort and Speed flyouts put a
   description on a second line, which does not fit DropdownItem's fixed
   height — the helper compensated with an !h-auto !py-2 override. Each flyout
   also repeated its own name as a sectionLabel title directly under the row
   that opened it.
4. The model row's icon lied. It wore the same ArrowRight01Icon chevron
   that every ActionSubmenu row uses to promise a flyout, but it dismisses the
   whole menu and hands off to the model picker.

The compact panel had two smaller inconsistencies: its IconButton renders a
4px corner against the neighbouring Button's 8px at the same 28px height, and
both glyphs used DROPDOWN_ITEM.iconSize (13px), which is sized for 32px
dropdown rows.

Solution

Drag feedback without changing commit semantics. EffortSlider gains an
optional onPreviewChange, reporting the level under the thumb mid-gesture and
undefined when it ends. ModelSettingsMenu holds that preview and passes it to
renderTrigger; the pill renders previewLevel ?? variant.level. onChange
still fires exactly once, on release — the alternative (committing per tick)
would push every intermediate model id through the caller's save path. The
preview is scoped to an open menu and cleared when the compact view unmounts,
since the slider cannot report the end of a gesture it is no longer mounted for.

Tone. The level steps up to text-primary-6 while the panel is open, and
returns to text-text-3 when closed. Ultra keeps text-purple-6 in both states
— that purple is a marker, not a de-emphasis.

Rows. choice() drops its description parameter and the !h-auto !py-2
override, so every radio row is a single-line DropdownItem again. Both section
titles are removed; ActionSubmenu already sets aria-label={label} on the
flyout panel, so each is still announced as "Speed" / "Effort".
standardDescription, fastDescription and ultraDescription become
unreferenced and are deleted from en and zh — the only two locales that
carried them.

The model row takes Search01Icon (the spotlight's own glyph, ICONS.search)
so the affordance matches the searchable picker it opens rather than promising a
flyout.

Compact panel polish. The advanced-settings button becomes
variant="tertiary" (borderless, quieter beside the Fast toggle) and is
relabelled from "Model settings" to "Switch model", reusing the existing
sessions:creator.switchModel key — it was translated in en/zh and had zero
consumers, so this retires a dead key instead of duplicating a string. The Fast
toggle takes rounded-lg to match the Button's 8px corner, both glyphs go to
16px, and the bolt fills (fill="currentColor" strokeWidth={0}, the same pattern
used for PlayIcon/PauseIcon elsewhere) while Fast is on.

The panel's anchor gap goes from the engine's 4px default to 10px, so the pill
stays readable under the panel while the slider is dragged.

Potential risks

• "Switch model" names a destination, not the click. That button still opens
  the advanced menu; it does not itself switch the model. The rename was
  requested with that behaviour explicitly left alone, but it is a wording/action
  mismatch a reviewer should weigh.
• The Ultra warning is gone. "Uses usage limits faster" was a real hint and
  the screenshot that prompted this only showed the Speed flyout. It was removed
  for consistency — keeping the description path alive for one caller would
  have kept the two-line row shape. Ultra is still marked by purple label and
  checkmark. Easy to restore if the hint is wanted.
• Preview/commit handoff. On release the preview clears and onChange fires
  in the same handler, so React batches them into one render. If a caller's apply
  path is asynchronous, the pill could show the pre-drag level for a frame. Not
  observed with the current callers, which update state synchronously.
• rounded-lg relies on Tailwind's emit order (rounded-lg after rounded
  in the border-radius group) rather than an ! prefix. This matches the
  existing WorkstationTrailTerminalHeader override, but it is a precedence by
  convention, not by specificity.
• The radius is fixed at one call site, not in IconButton. IconButton's
  base rounded (4px) matches no token in the codebase (DROPDOWN_ITEM is 6px,
  DROPDOWN_PANEL and Button are 8px) and 5 of its 22 call sites already
  override it. Changing the base would restyle 17 unreviewed surfaces, and 8px is
  wrong at the 20x20 sm size. The real fix is a size-scaled radius — a separate
  change.
• i18n. Deleting three keys is safe only because nothing references them;
  grep confirms zero consumers, and selectors.modelProperties.settings
  survives as the panel's aria-label.

Verification

Run against this branch in an isolated worktree checked out at its own commit
(not the shared dirty checkout), with node_modules symlinked:

• npx tsc --noEmit --pretty false -p tsconfig.json — exit 0.
• npx vitest run --config config/vitest.config.ts src/components/ModelSelectorPill src/components/ModelPropertiesDropdown
  — 3 files, 27 tests, all passing.
• npx eslint src/components/ModelSelectorPill/ src/components/ModelPropertiesDropdown/ — clean.
• npx prettier --check on the changed files — clean.
• Both edited locale files re-parse as valid JSON (json.load).

ModelSelectorPill.test.ts gains two tests:

• Single-line, untitled submenus and the model row's search glyph: the Speed
  flyout's text is exactly "StandardFast", the Effort flyout's first child is a
  level row rather than a heading, both keep their aria-label, and the model
  row's only svg carries data-icon="search". Also pins the tertiary classes
  and the Fast toggle's rounded-lg.
• Drag tracking and tone: drives a real pointerdown → range input →
  pointerup sequence, asserting the pill reads GPT 5.6 Sol Light mid-drag
  with apply not yet called, then commits gpt-5.6-sol-low on release; and
  that the level is text-text-3 at rest and text-primary-6 while open.

Every new assertion was mutation-checked — reintroducing a second line, a section
title, the chevron, the outlined button variant, the 4px corner, the preview, or
the open highlight each fails the corresponding test.

Not run / not applicable:

• No screenshots. ORG2 is a Tauri app with no browser-renderable entry point,
  so this panel cannot be captured without a full app launch. Behaviour is
  verified through jsdom rendering instead. This is the weakest part of the
  evidence here, since several changes are purely visual (icon size, bolt fill,
  corner radius, anchor gap); the tests pin the classes and attributes that
  produce them, not the rendered result.
• The anchor gap is not asserted — jsdom returns zero rects, so there is
  nothing meaningful to measure. It is a constant passed to useDropdownEngine.
• E2E was not run; no rendered spec covers this menu.
• No "Pre-commit hook ran." trailer. The commit was built with plumbing
  (temp index + commit-tree) so the unrelated uncommitted work in the shared
  checkout could not enter it. Hooks were skipped, so typecheck, lint and tests
  were run by hand as listed above. The hook's TypeScript gate cannot fail a
  commit anyway (TSC_OUTPUT=$(...) || true then $? is always 0).
• Base. Built on origin/develop (aa17dccd7). That commit's unused-export
  sweep (export interface ModelSelectorPillProps to interface ...) is
  preserved rather than reverted — the local checkout predates it.