feat: add generated scene skill platform hardening

docs/superpowers/reports/2026-04-18-g6-host-bridge-runtime-contract-report.md

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+# G6 Host Bridge Runtime Contract Report
+
+> Date: 2026-04-18
+> Scope: `G6` minimum runtime contract implementation
+
+## Summary
+
+`G6` has moved from pure fail-closed classification to a minimum runnable runtime contract.
+
+The implementation does not redesign the browser host transport. Instead it generates a conservative `host_bridge_workflow` script that:
+
+1. preserves host bridge actions
+2. preserves localhost host-runtime dependencies
+3. lists callback business endpoints
+4. invokes host bridge APIs when available
+5. invokes callback endpoints through the existing browser request path
+6. returns blocked/error/partial/ok artifact statuses instead of pretending full equivalence
+
+## Assets Updated
+
+1. `src/generated_scene/generator.rs`
+2. `tests/scene_generator_test.rs`
+
+## Contract
+
+The minimal `G6` contract is now:
+
+1. at least one `host_bridge` workflow step
+2. at least one `callback_request` workflow step
+3. at least one business endpoint
+
+If that contract is missing, generation still fails closed.
+
+## Validation
+
+Executed:
+
+```powershell
+cargo test --test scene_generator_test g6 -- --nocapture
+cargo test --test scene_generator_test -- --nocapture
+cargo test --test scene_generator_p1_family_test -- --nocapture
+cargo test --test scene_generator_family_policy_test -- --nocapture
+cargo test --test scene_generator_canonical_test -- --nocapture
+```
+
+All target regressions passed.
+
+## Result
+
+`G6` now has a minimum generated package path while retaining a fail-closed negative test for incomplete contracts.
+
+The next runtime-contract target is `G7 multi_endpoint_inventory`.