PT-4579: Percent stepper for the content-zoom default; Settings layout

[rolfheij-sil]

Stacked on #2803 (pt-4576-content-zoom-platform-core). Review only the commits above that branch. Stacked PRs get no automatic CI here; the full local battery (typecheck, lint, format:check, vitest run src: 263 files / 3833 tests) is green. After #2803 squash-merges this branch is rebased with git rebase --onto main <old parent tip>.

Summary

Work item 4 of the per-pane content-zoom epic (PT-4575): the Settings side of content zoom, plus the General / Supporter layout the Epic Lead agreed with UX on 2026-09-14.

• Percent stepper. platform.webViewContentZoom renders as − · 100 % · + · reset instead of a text box holding a decimal factor. A new renderer-internal PercentStepper (Button + lucide icons, role="group", localized aria-labels, aria-live readout, buttons disabled at the bounds and reset disabled at the default). It writes through the existing validate → setSetting tail without the text box's 500 ms debounce, so a press reaches following panes immediately (PT-3236 is sidestepped for this control only). Bounds, step and default come from the shared content-zoom constants; rounding follows the caller's step.
• Relabels. "Zoom factor" → Interface Scaling through a new key (%settings_platform_zoomFactor_label_2%, with a deprecation entry for the shipped key in metadata.json, per the Localization Guide's immutable-strings rule); "Zoom" → Tab content default zoom in place (never shipped); the content-zoom description is rewritten in percent terms and names Interface Scaling. Spanish keeps the two distinguishable ("Escalado de la interfaz" / "Zoom predeterminado del contenido de la pestaña"). platform.zoomFactor's control and behaviour are untouched (PT-3458 stays a no-go).
• Layout. General now reads Interface Language, Interface Scaling, Tab content default zoom (third, not first). A new Supporter settings group holds Request timeout and Show re-registration reminder at startup (keys, defaults and validators unchanged). Interface mode is hidden from Settings: its switch is the Simple/Power toggle in the profile popover, which the toolbar renders in both modes (user-profile-popover.component.tsx, platform-bible-toolbar.tsx), so a Settings entry would be a second switch for the same value.

Nothing zooms yet on its own: the default this control edits is applied by #2803 to panes that mark a zoom area, and the first such pane is PT-4581.

Why review this

Part of the current epic (PT-4575). This is the user-facing default for content zoom and the Settings relabel the PRD's terminology rule depends on.

Decisions worth a look

• The stepper does not call adjustZoomFactor. That helper hard-codes the shared step and bounds, which would make the component's min/max/step props decorative. It clamps to the props and rounds to the step's precision; the one call site passes the shared constants, so behaviour is identical.
• No optimistic readout. The stored value round-trips through the extension host before the prop updates, so two quick presses would both read the pre-press value. The readout always shows the stored value; only the arithmetic baseline for a rapid next press uses the last emitted factor, within a 1.5 s window and until the prop moves. Two earlier attempts at an optimistic readout each opened a stuck-or-flicker case (caught by the per-commit reviews), which is why the display is deliberately not optimistic.
• handleChangeSetting accepts a raw number for the stepper, next to the existing change-event, boolean and string-array cases, and is now a useCallback (it joined generateComponent's dependency list).
• "Interface Scaling" is title case as specified by UX, while the Localization Guide prescribes sentence case and the neighbouring labels are mixed. Left as specified; raise with UX if the house rule should win.
• Spanish strings added, not just relabelled: the Supporter group label ("Configuración de soporte", a translator may prefer another word for the supporter role) and the two registration-reminder strings that es.json had been missing, which the new group would otherwise show half in English.
• Studio's repo-patches/paranext-core.patch overrides the two relabelled keys and the General group metadata; that refresh belongs to PT-4585.
• No e2e changes needed. A broad grep of e2e-tests and the settings components found no assertion on the old labels or the General-group order; the zoom hits there are the Enhanced Resources media viewer, a different feature.

Testing

• Self-review: /review-paratext (four analyzer passes) and an OpenCodeReview delegate pass ran on the branch. One Critical (the in-place relabel of a shipped string, fixed via the new key) and the Important items are fixed here: tooltips on the three icon buttons and ButtonGroup per the Storybook guidelines, the glossary page, a story, the description in percent terms, and the stepper's readout following the stored value. Defaults applied without a ruling: "Interface Scaling" keeps UX's capital S although the capitalization guideline prefers sentence case; "Tab content default zoom" stays and its description explains it as the default for every pane in a tab; the Supporter group gained a description.
• New percent-stepper.component.test.tsx (19 cases: display, step up/down/reset, bounds, disabled, keyboard reachability, group label, optimistic double-press, prop catch-up, quarter and five-hundredths steps, tenth-step exactness).
• setting.component.test.tsx: the stepper renders for platform.webViewContentZoom and no text box; a press writes the stepped factor through setSetting; platform.zoomFactor still renders a text box.
• core-settings-info.data.test.ts: visible General order; Supporter group membership; moved settings keep keys, labels, defaults and validators; Interface mode hidden; every setting declared exactly once across groups.
• Root battery green (see the stacked note); shipped-locale-assets.test.ts green.
• roborev per-commit reviews triaged (one refuted: the group label key lands in the next commit of the same branch; one fixed: step-precision rounding).
• Manual check in the running app pending (Settings order, live stepper, both modes, Spanish).

Risk Level

Low–Medium. Relabels two visible settings and regroups two more; the new control is confined to one setting key.

AI-assisted — Claude Code (Fable 5.1 coordinating; Opus design pass; per-task Sonnet agents under TDD; Sonnet verification pass).

🤖 Generated with Claude Code

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This change is 

[rolfheij-sil]

🤖 Claude: Superseded by #2821, which combines this PR with the other content-zoom work items into one PR stacked on #2803. All commits are preserved there unchanged.