Add EAS Build cloud fallback to native_build for Android when local SDK is unavailable

[vincentvella]

Problem

native_build({ platform: "android" }) currently runs expo run:android, which requires a local Android SDK, adb, and a booted emulator. On developer machines without the Android SDK installed (a common setup for web-focused contributors, CI environments, or M-series Macs without full Android tooling), the build fails immediately with no useful fallback.

The README "Where to take it next" explicitly flags this gap: "an eas build fallback when there's no local native toolchain".

By contrast, iOS has a natural local path (Xcode + Simulator on macOS), so this gap is Android-specific.

Proposed Approach

Extend native_build with an optional mode parameter (or auto-detect):

native_build({ platform: "android", mode?: "local" | "eas" | "auto" })

• "local" (current behavior) — runs expo run:android; fails fast with a clear message if adb / SDK is absent.
• "eas" — runs eas build --platform android --profile development (or --profile preview), streaming output to the timeline. Requires eas-cli to be installed (npx eas-cli as fallback).
• "auto" (default) — probe for adb / a booted device first; fall back to eas if absent, surfacing a clear message explaining the switch.

The Settings → native readiness preflight (currently iOS+Android SDK checks) should surface EAS CLI availability alongside SDK presence so the agent and user know which path will be taken.

Streaming output should land on the timeline the same way expo run:android output does today (same native source, same dev_start-style line-by-line tee).

Affected Files

• src/toolSpecs.ts — extend native_build schema with mode param
• src/toolLayer.ts — native_build handler logic
• src/reactNativeController.ts — Android build orchestration
• cockpit/main.ts — native readiness preflight UI integration

[vincentvella]

Tracked in Linear (the planning hub) — GitHub Issue Sync has been retired. Closing this orphaned mirror; the work is relocated, not abandoned.