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/WP-33-dev-switchers.md

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+# WP-33 — In-app dev switchers (scenario + role)
+
+Status: done
+Phase: 7 — refinements
+
+## Why
+
+The two dev-only stand-ins — the async `?scenario=` toggle (`scenario.interceptor.ts`) and the
+faked `?role=` (`role.interceptor.ts`) — were driven by hand-editing the URL query string.
+Awkward for demos: you had to remember the valid values and retype them. This WP surfaces both
+as dropdowns in the existing dev panel so a scenario/role can be flipped with a click.
+
+## Decisions (pre-made, don't relitigate)
+
+- **No new component/shell wiring.** The switchers live inside the existing `debug-state`
+  devtool (the sanctioned dev-only fab/panel already mounted in the shell under `isDevMode()`).
+- **Reuse the mechanism modules, don't duplicate their source of truth.** `scenario.ts`/`role.ts`
+  gain a `set*` setter + an exported valid-values list; the panel imports them. `debug-state` is
+  added to the `ui→infrastructure` eslint exemption (same precedent as its existing cross-context
+  exemption) rather than re-declaring the storage keys / valid lists in the UI.
+- **Scenario becomes tab-sticky (sessionStorage), mirroring role.** Without this the switcher
+  would be near-useless: navigation drops the query param and reverts to `default` mid-demo.
+- **Apply by `location.reload()`.** Both values are read per-request in interceptors and gate
+  server-computed decision flags already fetched by eager `httpResource`s — a reload is the
+  simplest correct way to re-run them. Acceptable for a dev tool.
+
+## Files
+
+- `shared/infrastructure/scenario.ts` — tab-sticky read (mirrors role), `setScenario`, exported
+  `SCENARIOS`; co-located `scenario.spec.ts`.
+- `shared/infrastructure/role.ts` — `setRole`, exported `ROLES`.
+- `shared/ui/debug-state/debug-state.component.ts` — two `<select>`s in the panel.
+- `eslint.config.mjs` — extend the debug-state devtool exemption to the ui→infrastructure rule.
+
+## Acceptance criteria
+
+- [x] Dev panel shows role + scenario dropdowns; changing one persists it and reloads.
+- [x] Scenario survives navigation within the tab (sticky).
+- [x] `npm run ci` green (lint, tests incl. new scenario spec, localized build).