feat: add generated scene skill platform hardening

docs/superpowers/specs/2026-04-19-boundary-fail-closed-decision-design.md

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+# Boundary Fail-Closed Decision Design
+
+> Date: 2026-04-19
+> Status: Draft
+> Parent Framework Plan: `docs/superpowers/plans/2026-04-19-scene-skill-102-full-coverage-framework-plan.md`
+> Parent Route: `Route 5: boundary-family fail-closed`
+> Parent Layer: `Layer C + Layer D`
+
+## Intent
+
+Inspect the remaining boundary-family fail-closed records and decide whether they should be:
+
+1. deferred
+2. kept as boundary fail-closed
+3. opened into one bounded correction slice
+
+This is a decision-first route.
+
+## Fixed Input Bucket
+
+1. `local_doc_pipeline = 5`
+2. `host_bridge_workflow = 1`
+3. `page_state_eval/bootstrap_target = 1`
+
+## Allowed Files
+
+1. boundary decision JSON assets
+2. boundary decision report assets
+3. optional next-plan design/plan files only if a bounded boundary slice is justified
+
+## Forbidden Files
+
+1. `src/generated_scene/analyzer.rs`
+2. `src/generated_scene/generator.rs`
+3. `tests/fixtures/generated_scene/scene_execution_board_2026-04-18.json`
+
+## Expected Delta
+
+1. no code-level coverage delta is required
+2. the expected result is a decision-quality delta:
+   - defer
+   - hold
+   - open one bounded slice
+
+## Stop Rule
+
+Stop after the boundary decision is published.
+
+Do not start boundary implementation under this plan.
+