Editor S10: Refactor android.yml/package.yml to call scaffolded scripts

[mblackman]

P2.

CI workflows currently duplicate build logic that also lives in the editor's Export Build path. Refactor .github/workflows/android.yml and package.yml to invoke the same scaffolded scripts emitted by octarine init-build-scripts (#49) — the editor (#74) and CI then share one build code path. Single source of truth: whatever CI runs, a dev can run locally by hand.

Scope:

• Replace inline build steps in android.yml / package.yml with calls into the scaffolded scripts/ (build, bake/manifest, package)
• Keep CI-only concerns (matrix, secrets, artifact upload) in YAML; push buildable logic into the scripts
• Verify parity: editor Export Build (Editor S5: Export Build button #74) and CI produce equivalent artifacts

Depends on #49 (scaffolder), #74 (export build). Parent: #45.