feat(android): route plugin.json scripts through segkit (#58)

Replace direct android.sh calls in the Android plugin's convenience
scripts with segkit android delegation. No fallbacks — segkit must be
available on PATH or the command fails immediately.

Scripts updated: android:sync, android:devices:eval, start:android,
start:emu, stop:emu, reset:emu.

Also adds `segkit:install` devbox script for cargo install --path.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: abueide

devbox.json

@@ -199,6 +199,9 @@
       "segkit:build": [
         "cargo build --manifest-path segkit/Cargo.toml"
       ],
+      "segkit:install": [
+        "cargo install --path segkit"
+      ],
       "segkit:test": [
         "cargo test --manifest-path segkit/Cargo.toml"
       ],

plugins/android/plugin.json

@@ -73,22 +73,22 @@
         "bash {{ .Virtenv }}/scripts/user/setup.sh"
       ],
       "android:sync": [
-        "android.sh devices sync"
+        "segkit android devices sync"
       ],
       "android:devices:eval": [
-        "ANDROID_SDK_REQUIRED=0 android.sh devices eval"
+        "ANDROID_SDK_REQUIRED=0 segkit android devices eval"
       ],
       "start:android": [
-        "android.sh run \"${1:-}\""
+        "segkit android run \"${1:-}\""
       ],
       "start:emu": [
-        "android.sh emulator start \"${1:-}\""
+        "segkit android emulator start \"${1:-}\""
       ],
       "stop:emu": [
-        "android.sh emulator stop"
+        "segkit android emulator stop"
       ],
       "reset:emu": [
-        "android.sh emulator reset"
+        "segkit android emulator reset"
       ],
       "doctor": [
         "bash {{ .Virtenv }}/scripts/user/doctor.sh"