feat: add generated scene skill platform hardening

docs/superpowers/specs/2026-04-19-g6-host-bridge-prerequisites-design.md

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+# G6 Host-Bridge Prerequisites Design
+
+> Date: 2026-04-19
+> Status: Draft
+> Upstream Decision: [2026-04-19-boundary-runtime-prerequisites-decision-report.md](D:/data/ideaSpace/rust/sgClaw/claw-new/docs/superpowers/reports/2026-04-19-boundary-runtime-prerequisites-decision-report.md)
+
+## 1. Intent
+
+This design defines the next bounded slice after the boundary-runtime prerequisites roadmap selects `G6 host-bridge prerequisites`.
+
+The target is:
+
+`G6 host-bridge prerequisites`
+
+## 2. Why G6 First
+
+`G6` is selected because:
+
+1. it is blocked by one clearer prerequisite line
+2. that prerequisite line is narrower than the combined local-doc and attachment burden on `G8`
+3. it is the smaller bounded next step after `G7`
+
+## 3. Scope Boundary
+
+This design is limited to prerequisite scoping only.
+
+It may include:
+
+1. isolating the minimum host-bridge execution semantics needed before `G6` real-sample entry
+2. defining a bounded prerequisite slice
+3. publishing one follow-up bounded plan
+
+It must not include:
+
+1. executing a `G6` real sample
+2. implementing host-runtime directly
+3. reopening `G7`
+4. opening `G8`
+5. opening `G4 / G5`
+
+## 4. Target Outcome
+
+The bounded target outcome is one state:
+
+1. one bounded `G6` prerequisites plan
+
+## 5. Exit Condition
+
+This design is complete when implementation can be bounded to one plan that:
+
+1. freezes the `G6` prerequisite boundary
+2. isolates the minimum blocked host-bridge capability
+3. publishes a bounded follow-up plan