feat(Android, Stack v5): add title/subtitle font customization

[kligarski]

Description

Adds support for customizing text appearance for title and subtitle in header.

Closes https://github.com/software-mansion/react-native-screens-labs/issues/909.
Closes https://github.com/software-mansion/react-native-screens-labs/issues/910.

Typeface resolution

In order to keep separation between React and native side, I decided to handle the font as follows:

1. Applicator resets the font to Material's default.
2. Applicator asks the ConfigurationProviding to apply any changes to the default font via titleTypefaceTransform function.
3. HeaderConfig which implements ConfigurationProviding uses ReactTypefaceUtils.applyStyles to modify the font family, style and weight and returns modified Typeface
4. Applicator applies the returned Typeface

Changes

• add props and handle them on the native side:
  • small header: {title,subtitle}{Color,FontFamily,FontSize,FontWeight,FontStyle}
  • medium/large header: {collapsed,Expanded}{Title,Subtitle}{Color,FontFamily,FontSize,FontWeight,FontStyle}
• add TITLE_APPEARANCE invalidation flag to StackHeaderConfig
• add StyleUtils.resolveStyleResAttr to resolve default text appearance
• add View.spToPx extension that allows to convert SP to pixels with respect to view's display metrics
• add invalidatingProperty util to StackHeaderConfig for props that invalidate a flag on diff
• add SFT

Before & after - visual documentation

small	medium/large
small.mp4	large.mp4

Test plan

Run test-stack-header-title-appearance-android.

Checklist

• Included code example that can be used to test this change.
• For visual changes, included screenshots / GIFs / recordings documenting the change.
• For API changes, updated relevant public types.
• Ensured that CI passes

[Copilot]

Pull request overview

Adds Android Stack v5 (Material 3) header support for customizing title/subtitle text appearance (color, size, family, weight, style) for both small headers and expanded/collapsed states in medium/large collapsing headers, wiring new JS props through Fabric to native applicators and providing a manual SFT scenario to validate behavior.

Changes:

• Exposes new android props for title/subtitle appearance (small + expanded/collapsed variants) and stringifies fontWeight on the JS side for the native setter contract.
• Implements Android-side appearance application with a new TITLE_APPEARANCE invalidation flag, default text-appearance reset via theme attrs, and typeface transforms via ReactTypefaceUtils.
• Adds utilities (resolveStyleResAttr, View.spToPx) and a new single-feature-test scenario for manual verification.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/fabric/stack/StackHeaderConfigAndroidNativeComponent.ts	Adds new native props for title/subtitle appearance (small + expanded/collapsed variants).
src/components/stack/header/StackHeaderConfig.android.types.ts	Updates public TS types/docs to expose new Android header appearance props.
src/components/stack/header/StackHeaderConfig.android.tsx	Converts fontWeight values to strings before passing to native.
apps/src/tests/single-feature-tests/stack-v5/test-stack-header-title-appearance-android/scenario.md	Adds manual test scenario documentation for verifying appearance behavior.
apps/src/tests/single-feature-tests/stack-v5/test-stack-header-title-appearance-android/scenario-description.ts	Registers scenario metadata for the new SFT.
apps/src/tests/single-feature-tests/stack-v5/test-stack-header-title-appearance-android/index.tsx	Implements the interactive SFT UI to exercise all appearance props.
apps/src/tests/single-feature-tests/stack-v5/index.ts	Exports/registers the new scenario in the Stack v5 SFT group.
android/src/main/java/com/swmansion/rnscreens/utils/StyleUtils.kt	Adds helper to resolve theme style attributes to concrete style resource IDs.
android/src/main/java/com/swmansion/rnscreens/utils/DimensionUtils.kt	Adds View.spToPx for font-size conversion respecting view display metrics/font scale.
android/src/main/java/com/swmansion/rnscreens/stack/header/StackHeaderCoordinatorLayout.kt	Hooks new TITLE_APPEARANCE invalidation into the update pipeline.
android/src/main/java/com/swmansion/rnscreens/stack/header/StackHeaderApplicator.kt	Applies title/subtitle appearance (reset-to-default + overrides) for small and collapsing headers.
android/src/main/java/com/swmansion/rnscreens/stack/header/config/StackHeaderInvalidationFlags.kt	Introduces TITLE_APPEARANCE flag and includes it in APPEARANCE.
android/src/main/java/com/swmansion/rnscreens/stack/header/config/StackHeaderConfigViewManager.kt	Adds setters for all new appearance props, parsing weight/style via ReactTypefaceUtils.
android/src/main/java/com/swmansion/rnscreens/stack/header/config/StackHeaderConfigurationProviding.kt	Extends config contract with appearance-related values and TypefaceTransform.
android/src/main/java/com/swmansion/rnscreens/stack/header/config/StackHeaderConfig.kt	Stores new appearance props, builds TypefaceTransforms, and adds invalidatingProperty helper.
android/src/main/java/com/swmansion/rnscreens/stack/header/appbar/StackHeaderAppBarLayout.kt	Forces creation of stable title/subtitle TextView references for small header toolbars.

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[t0maboro]

if we're clearing the text anyway, won't it work to have two distinct placeholders rather than these checks ?

[t0maboro]

won't it allocate a new lambda object on every call?

[t0maboro]

Seems to be the same set of props as for the title - shouldn't we consider some grouping inside a dedicated object and operate on e.g. title/subtitleAppearance objects on the native side?

[t0maboro]

nit: codegen handles that default properly, but in other places we're using CT.WithDefault<CT.Float, -1.0>;