docs(release): cross-platform flag-stripping verification runbook

[kirich1409]

Goal

Document an end-to-end runbook for verifying that local-flag-guarded code is stripped from release builds of each sample app: :sample:android-app, :sample:desktop, and iosApp/.

Context

Shrinker / DCE tests cover the generators and tooling level:

• Android R8: tracked by Automated R8 DCE verification for feature flags #153 (closed); generator build-logic/featured-gradle-plugin/.../ProguardRulesGenerator.kt; tests in featured-shrinker-tests.
• iOS Swift DCE: covered by xcconfig generator; automated test tracked by the iOS DCE verification follow-up issue.
• JVM/Desktop: covered by the same plugin output; automated test tracked by the JVM shrinker follow-up issue.

What is missing is a consumer-visible procedure: "build this sample in release mode and confirm a disabled flag's UI does not appear in the bundle."

Scope

• New section in the Release Optimization wiki page (or a dedicated Verification subpage), one runbook per platform.
• For each platform: minified-release build command, where to find the artifact, how to inspect it (apkanalyzer / unzip + javap / nm + swift demangle).
• Reference disabled flags from :sample:feature-* modules so the steps reproduce against the real sample state.
• Stretch: a GitHub Actions workflow that runs the runbook checks on every push to develop.

Definition of Done

• Wiki page lists a runbook per platform (manual steps minimum)
• Cross-references to the automated shrinker tests
• Optional: workflow runs the runbook on develop (macOS for iOS; Linux for Android/Desktop)

Related

• iOS Swift DCE automated test (sibling issue)
• JVM/Desktop shrinker automated test (sibling issue)
• Automated R8 DCE verification for feature flags #153 (Android R8 — closed)