feat: add generated scene skill platform hardening

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

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+# G6 Host-Bridge Callback Semantics Design
+
+> Date: 2026-04-19
+> Status: Draft
+> Upstream Report: [2026-04-19-g6-host-bridge-execution-semantics-report.md](D:/data/ideaSpace/rust/sgClaw/claw-new/docs/superpowers/reports/2026-04-19-g6-host-bridge-execution-semantics-report.md)
+
+## 1. Intent
+
+This design defines the next bounded slice after `G6 host-bridge execution semantics`.
+
+The target is:
+
+`G6 host-bridge callback semantics`
+
+## 2. Why This Slice
+
+The previous semantic slice isolated two seams, but the tighter next pressure is callback-side semantics:
+
+1. invocation semantics are already identified
+2. callback completion semantics still determine whether later real execution can be bounded safely
+
+## 3. Scope Boundary
+
+This design is limited to callback semantics only.
+
+It may include:
+
+1. defining completion states for callback requests
+2. defining blocked/error/partial/ok transitions
+3. defining how callback semantics constrain later real-sample entry
+
+It must not include:
+
+1. implementing host-runtime directly
+2. executing a `G6` real sample
+3. reopening `G7`
+4. opening `G8`
+
+## 4. Target Outcome
+
+The bounded target outcome is one state:
+
+1. one bounded `G6 host-bridge callback semantics` plan
+
+## 5. Exit Condition
+
+This design is complete when implementation can be bounded to one plan that:
+
+1. freezes callback semantics only
+2. separates completion state logic from transport/runtime implementation
+3. emits one bounded follow-up plan