Templates: vendor_usb peripheral block in Android codegen

[HeroesLament]

Templates side of Mob.VendorUsb (companion runtime/NIF/SDK in mob#5).

Wires generated Android project to expose USB host for vendor-class devices (AtomVM ESP32 modems, custom HID, FTDI, industrial sensors, lab equipment).

Files

MobBridge.kt.eex (+309)

• 7 @JvmStatic methods: vendor_usb_list_devices, request_permission, open, bulk_write, start_reading, stop_reading, close
• Bulk-IN reader thread per session, posts :data events back to BEAM
• BroadcastReceiver for ACTION_USB_PERMISSION
• jmethodID cache slots for nativeDeliverVendorUsbOpened / Permission / Event / Data
• All 7 methods wrapped in try { ... } catch (e: Exception) { ...nativeDeliverVendorUsbEvent(pid, -1, \"error\", \"exception\") } matching existing camera_* / audio_* convention. Unhandled JVM exception in JNI = BEAM dies, no crash dump. Defense caught 2 nil-encoding bugs during testing.
• vendor_usb_list_devices uses optInt(name, default) — defends against Elixir nil → JSON string \"nil\" (which getInt chokes on, throwing JSONException → unhandled → BEAM dies).

beam_jni.c.eex (+58)

• 7 native trampolines forwarding to matching mob_nif.c entry points.

AndroidManifest.xml.eex (+6)

• uses-feature android:name=\"android.hardware.usb.host\" android:required=\"false\" — declares optional USB host so Play Store doesn't filter app off non-USB devices; runtime ACTION_USB_PERMISSION still gates per-device access.

Tested

Generated project with these templates, deployed to OnePlus CPH2451 (Android 16). Full lifecycle confirmed against real vendor-class device (AtomVM ESP32 + Taixin TX-AH HaLow modem):

• list_devices returns device JSON
• request_permission triggers system dialog → permission_granted_json envelope
• open returns session ID
• start_reading + bulk_write round-trip ETF length-prefixed frames
• close releases interface cleanly
• All 7 try/catch wrappers exercised by deliberately malformed input — error envelopes delivered, BEAM survives.

[GenericJam]

Holding this open alongside mob#5. Companion runtime PR can't merge as-is — Android NIF surface migrated from C to Zig after both PRs were opened (see comment on mob#5). This templates PR will land together with the rebased runtime PR. The Kotlin/JNI work here is unaffected by that migration; only the C-side glue needs porting.

[GenericJam]

Tracked under GenericJam/mob#6 (porting plan for the companion runtime PR). The templates side here is structurally fine; it'll land alongside the rebased runtime PR.

[GenericJam]

Update: the runtime side of vendor_usb landed in GenericJam/mob#a3a1ed6 (closes #6). The Zig port adopts a cacheOptional model — on the unmodified template, MobBridge lookups for vendor_usb_* fail gracefully and the BEAM emits :unsupported events instead of crashing. So this templates PR is no longer a hard blocker for vendor_usb being merged into mob proper, but it IS still the gate for end-to-end functionality on Android (the Kotlin side that this PR adds is what actually talks to UsbManager).

This PR should still merge clean against current master (it predates the C → Zig migration on the runtime side; templates side is unchanged shape). Will pick it up in a follow-up pass.