feat(browser): W4-C BrowserProvider contract and camofox-browser adapter skeleton

- contracts/browser.ts: provider kind, per-capability {supported, verified} flags,
  session/tab/control-lease rows, NavigationBudget, redacted BrowserSnapshot,
  DownloadArtifact with blob/secret refs, BrowserErrorKind
- adapters/browser: BrowserProvider interface, camofox client (health, capabilities
  static + /openapi.json probe, openSession/navigate/snapshot/screenshot; rest
  not_implemented for M2), none provider, redactSnapshot, profile serial lock,
  domain allowlist budget; Bearer access key via BrowserSecretResolver
- testkit/browser: mock camofox server (auth, fixtures with secrets, faults)
- db 0023: browser_provider/session/tab/control_lease with one-active-lease and
  one-live-session-per-profile partial unique indexes; types regenerated
- docs/design/browser-provider.md: contract, camofox OpenAPI 1.17.0 mapping,
  unverified items and M2 prototype checklist; Playwright is not a product browser

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/contracts/test/db-sync.test.ts

@@ -88,6 +88,11 @@ const ROWS: Record<string, { row: Obj; dbOnly?: string[]; apiOnly?: string[] }>
   MetadataField: { row: C.MetadataField },
   ResolutionAttempt: { row: C.ResolutionAttempt },
   SiteSnapshot: { row: C.SiteSnapshot },
+  // W4-C 浏览器实体(0023)
+  BrowserProvider: { row: C.BrowserProviderRow },
+  BrowserSession: { row: C.BrowserSession },
+  BrowserTab: { row: C.BrowserTab },
+  BrowserControlLease: { row: C.BrowserControlLease },
 };
 
 /** 引擎自有表(@umt/tasks 内部使用,不经 API 暴露),不要求 Row schema */
@@ -209,6 +214,13 @@ const ENUMS: Record<string, z.ZodEnum> = {
   ResolutionAttemptActorType: C.ActorType,
   SiteSnapshotKind: C.SiteSnapshotKind,
   SiteSnapshotStatus: C.SiteSnapshotStatus,
+  // W4-C(0023)
+  BrowserProviderKind: C.BrowserProviderKind,
+  BrowserProviderHealthStatus: C.InstanceHealth,
+  BrowserSessionController: C.BrowserController,
+  BrowserTabStatus: C.BrowserTabStatus,
+  BrowserControlLeaseHolderKind: C.BrowserLeaseHolderKind,
+  BrowserControlLeaseStatus: C.BrowserLeaseStatus,
 };
 
 describe("contracts ⇔ db 表结构同步", () => {