feat(dev): WP-33 — in-app dev switchers for scenario + role

Surface the ?scenario= and ?role= dev stand-ins as dropdowns in the existing
debug-state devtool, so a demo can flip them with a click instead of editing the
URL. scenario.ts/role.ts gain set* setters + exported valid-value lists (reused
by the panel, no duplicated source of truth); scenario becomes tab-sticky like
role so it survives navigation. Applied via location.reload() since both are
read per-request in interceptors. Extends the debug-state eslint exemption to the
ui→infrastructure rule (same devtool precedent).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/project/backlog/README.md

@@ -77,7 +77,7 @@ for its existing violations, so every WP ends green.
 | [WP-30](WP-30-ci-perf-followups.md)        | CI performance follow-ups (node_modules cache, runner image, path filters)        | follow-on · CI/infra        | todo   |
 | [WP-31](WP-31-shared-store-helpers.md)     | Shared store helpers (ActionState/SaveState, history, debounced-save, RemoteData) | 7 · refinements             | done   |
 | [WP-32](WP-32-stamdata-undo.md)            | Undo/redo in the stamdata editor                                                  | 7 · refinements             | done   |
-| [WP-33](WP-33-dev-switchers.md)            | In-app dev switchers (scenario + role)                                            | 7 · refinements             | todo   |
+| [WP-33](WP-33-dev-switchers.md)            | In-app dev switchers (scenario + role)                                            | 7 · refinements             | done   |
 | [WP-34](WP-34-adres-phone-brp-readonly.md) | Adres: phone field + BRP address read-only                                        | 7 · refinements             | todo   |
 | [WP-35](WP-35-one-concept-per-type.md)     | One Concept per case type (server-enforced)                                       | 7 · refinements             | todo   |
 | [WP-36](WP-36-admin-cases.md)              | Admin cases page + admin delete                                                   | 7 · refinements             | todo   |