C6: Migrate templates — generated packages are v2-native and Effect-first #29

Parent Part of #23 (Spec: opencode-architect 1.0.0) ## What to build The scaffolding templates the packager and publisher render are migrated so generated packages are v2-native: Effect-first plugin entry and config templates, v2-native registration snippets, v2 permission shapes, refreshed dependency ranges (no stale v1 pins), and the content declaration concept unchanged. Generated packages pass their own gates after rendering. ## Acceptance criteria - [x] Rendered package's plugin entry uses the v2 Effect API - [x] Rendered configs and registration snippets are v2-native - [x] Dependency ranges verified current per the verified-facts record - [x] Rendered package passes its own typecheck, tests, and install gates - [x] Template tests migrated and green ## Blocked by - #C4