feat(ui): preserve platform setup canonical routes

docs/modules/ui/platform-setup-canonical-route-preservation/README.md

@@ -0,0 +1,46 @@
+# Platform Setup Canonical Route Preservation
+
+## Purpose
+- Keep `/ops/platform-setup/*` as a stable canonical route family while the shared setup/topology cutover continues.
+- Preserve bookmarked operator entry points without forking the actual setup behavior into a second product shell.
+
+## Canonical Owner
+- Owner shell:
+  - `Ops > Platform Setup`
+- Preserved canonical leaf routes:
+  - `/ops/platform-setup`
+  - `/ops/platform-setup/regions-environments`
+  - `/ops/platform-setup/promotion-paths`
+  - `/ops/platform-setup/workflows-gates`
+  - `/ops/platform-setup/gate-profiles`
+  - `/ops/platform-setup/release-templates`
+  - `/ops/platform-setup/policy-bindings`
+  - `/ops/platform-setup/defaults-guardrails`
+- Shared setup/trust destinations still owned elsewhere:
+  - `/setup/topology/*`
+  - `/setup/trust-signing`
+
+## Route Contract
+- `ops/platform-setup/*` must render their intended platform-setup pages without rewriting the browser URL to `setup/topology/*`.
+- Explicit drill-ins into the broader topology product may still link to `/setup/topology/*` when the destination has no canonical `ops/platform-setup` equivalent.
+- `trust-signing` stays a redirect into `Setup > Trust & Signing`; it is not owned by `Platform Setup`.
+
+## Preserved Value
+- Keep:
+  - stable operator bookmarks for legacy platform-setup leaves
+  - the lighter platform-setup summaries for regions, promotion paths, workflows, and gate profiles
+  - a clear distinction between the `Ops > Platform Setup` handoff shell and the broader `Setup > Topology` workspace
+- Why:
+  - these leaves are still referenced from live setup and ops surfaces
+  - the defect was URL drift, not missing product value
+
+## Shipped In This Cut
+- Replaced redirect-only platform-setup topology leaves with mounted canonical pages.
+- Updated Platform Setup home quick links to stay on `/ops/platform-setup/*`.
+- Repaired stale page-local `/platform/setup/*` and `/topology/*` links to either canonical platform-setup leaves or valid setup/topology drill-ins.
+- Added focused Angular and Playwright regression coverage for preserved canonical URLs.
+
+## Related Docs
+- `docs/features/checked/web/platform-setup-canonical-route-preservation-ui.md`
+- `docs/features/checked/web/topology-trust-administration-ui.md`
+- `docs/modules/ui/topology-trust-administration/README.md`