feat(diagnostics): the debug recorder — start, the pill, steps, screenshots, stop (E16 S2)

- the start dialog is the consent: level (Részletes/Teljes), what is recorded,
  retention and the cap (now served as diagnostics.session_minutes)
- the pill docks under the toasts: elapsed time, Step (an optional label,
  its own Escape layer), Screenshot (tab capture where the browser has it),
  Stop; compact on a phone
- while recording, lib/log tags every event and every request path (req,
  beacon, uploadReq via one identityHeaders) names the session; applyDiagnostics
  raises the level for the session's run and never lowers a raised one, and
  lapses at whichever ends first
- Stop sends what is waiting before the server closes the session; the cap
  says so and opens the composer
- Settings → Diagnosztika and the command palette start/step/stop it
- the evidence leaves the log upload's own request lines out
- the step shortcut is deliberately palette-only: the keymap's D1 rule bars a
  new modifier chord, and a bare letter collides with the players'

frontend/src/lib/api.ts

@@ -68,7 +68,7 @@ import { messagingApi } from "./api/messaging";
 export type * from "./api/messaging";
 import { downloadsApi } from "./api/downloads";
 export type * from "./api/downloads";
-import { diagnosticsApi } from "./api/diagnostics";
+import { debugSessionsApi, diagnosticsApi } from "./api/diagnostics";
 export type * from "./api/diagnostics";
 export { DIAGNOSTICS_EVENTS_PATH } from "./api/diagnostics";
 
@@ -90,4 +90,5 @@ export const api = {
   ...messagingApi,
   ...downloadsApi,
   ...diagnosticsApi,
+  ...debugSessionsApi,
 };