generated-scene: add scheduled monitoring runtime and helper lifecycle hardening

tests/fixtures/generated_scene/p0_canonical_answers/README.md

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+# P0 Canonical Answers
+
+This directory stores repo-local canonical answer baselines for the
+`2026-04-17-scene-skill-60-to-90-roadmap` execution line.
+
+These assets are not a claim that the full external production scenes are
+already checked into this repository. They are the in-repo equivalent
+golden baselines used to keep three P0 archetypes stable during regression:
+
+- `p0-1-tq-lineloss-report.scene-ir.json`
+  Repo-local `multi_mode_request` canonical aligned to the `tq` benchmark role.
+- `p0-2-single-request-table.scene-ir.json`
+  Repo-local `single_request_table` canonical for generic single-request reports.
+- `p0-3-paginated-enrichment.scene-ir.json`
+  Repo-local `paginated_enrichment` canonical for list-detail enrichment flows.
+
+The current execution phase uses these files as golden `Scene IR` references
+until full external P0 source packages are brought into a controlled fixture set.