Harden Android Blockly runtime and test isolation

[yyods]

Summary

• make the Android manifest explicit about BLE hardware, Android 12+ permissions, legacy permission caps, and the temporary Lenovo/MediaTek Impeller fallback
• preserve the GPIO chooser's text-input identity across keyboard insets and make Blockly generation an explicit Preview/Create/Replace action
• bind Blockly bridge traffic to a per-page host epoch, serialize native WebView setup, retry failed readiness safely, and ignore stale reload traffic
• recognize Blockly's canonical {} serialization as an empty workspace
• isolate Android integration tests under dev.pyble.pyble.integrationtest while compiling and auditing the normal production package separately in CI
• freeze the behavior in the app specifications and add unit, widget, integration, asset, and CI-contract coverage

Why

Android validation exposed several independent failure modes:

• Flutter 3.44 Impeller/Vulkan rendered a blank foreground frame on the Lenovo TB-J616X / MediaTek Android 12 device.
• The GPIO chooser could replace its effective input client during keyboard-driven responsive rebuilds, while per-keystroke WebView generation added avoidable native-platform churn.
• Blockly readiness and later messages were not tied to the document generation that emitted them, so reloads and delayed traffic could affect the current host.
• Device-test installation and cleanup reused the normal launcher application ID.
• Blockly serializes a truly empty workspace as {}, which the native empty-state check did not recognize.

Impact

The normal Android launcher remains dev.pyble.pyble. Device tests now use the disposable integration flavor, so they cannot replace or uninstall a user's PyBLE installation. GPIO edits stay native and focused until the user requests generation, and reload traffic is generation-scoped.

The production-flavor APK is still signed with Gradle's debug configuration. It is a local development artifact, not a public beta or release.

Validation

• flutter test --exclude-tags golden: 649 passed
• focused Android/Blockly regression set: 106 passed
• flutter analyze: clean
• Blockly Node asset smoke: passed
• publication CI contract: 8/8 passed
• no-leak, SPDX, import-boundary, locale-parity, formatting, DCO, and diff checks: passed
• production APK built as dev.pyble.pyble; isolated test APK built as dev.pyble.pyble.integrationtest
• production APK contains no integration-test payload and verifies with the expected Android Debug certificate
• manual Lenovo TB-J616X / Android 12 validation connected to a classic ESP32 and ran Blink an LED on GPIO 2 to Finished with a physical blink; the same Android implementation also connected to an ESP32-S3 module and ran Blink a NeoPixel on its onboard GPIO 48 pixel

Scope

This PR is based on the current public main lineage. The local CNX correspondence draft, legacy announcement kit/assets, datasheet, and unrelated MicroPython submodule work are intentionally excluded.