Docs: Android support across README + docs/* + CHANGELOG #43

Final slice of #32. Reflect Android shipping across the user-facing docs.

Scope

• README.md: Android row in the platform table → "Shipping (Fabric / New Architecture)" with min API 24. Quick-start mention of Sora-Editor as the Android backing library. Repo layout: `android/` is no longer a stub; `example/expo-app/` covers iOS + Android, `example/macos-app/` is bare-RN-only. Roadmap: drop "Android (TextKit alternative)" — it's done.
• docs/installation.md: Android section under platform deployment targets. `minSdk 24` (Sora's floor + RN baseline). Note the LGPL-2.1 inheritance from Sora-Editor — consumers MUST keep it as an unmodified Gradle `implementation` dep (no shading / forking). Document that our app.plugin.js auto-injects `coreLibraryDesugaring` so consumers don't hand-edit `android/app/build.gradle`.
• docs/usage.md: confirm the props table calls out which props work where; Android now matches iOS for all of them after feat(android): font, contentInsets, lineNumbers (closes #37, refs #32) #38 + feat(android): theme prop — light / dark / auto (closes #39, refs #32) #40.
• docs/examples.md: Android row in the platform-examples table (iOS + Android share the Expo CNG `example/expo-app/` example).
• CHANGELOG.md: `Unreleased` entry covering Android shipping (PRs feat(android): TextMate syntax highlighting (closes #35, refs #32) #36, feat(android): font, contentInsets, lineNumbers (closes #37, refs #32) #38, feat(android): theme prop — light / dark / auto (closes #39, refs #32) #40, ci: android + macos build jobs, fix iOS paths (closes #41, refs #32) #42).

Refs #32. After this lands, #32 closes.