chore(types): fewer any casts; eslint warning ratchet 36 -> 29 (#210)

- Developer tools (send event, state event editor, room account data) and
  setMarkedUnread go through the typed helpers in utils/room and
  utils/accountData (new setRoomAccountData) instead of casting at the
  call site; sendStateEvent accepts a developer-chosen type string.
- SecretStorage passes the key description as the SDK's
  SecretStorageKeyDescription, CallEmbed replies with an IWidgetApiRequest,
  and fillMissingPowers writes through a Record instead of `as any`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

package.json

@@ -12,7 +12,7 @@
     "build": "vite build",
     "preview": "vite preview",
     "lint": "npm run check:eslint && npm run check:prettier",
-    "check:eslint": "eslint src/* --max-warnings 36",
+    "check:eslint": "eslint src/* --max-warnings 29",
     "check:prettier": "prettier --check .",
     "fix:prettier": "prettier --write .",
     "typecheck": "tsc --noEmit",