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/adapters/src/browser/none.ts

@@ -0,0 +1,46 @@
+import type { BrowserCapabilities, BrowserCapabilityFlag, BrowserHealth } from "@umt/contracts";
+import { BROWSER_CAPABILITY_KEYS } from "@umt/contracts";
+import { BrowserError } from "./errors.ts";
+import type { BrowserProvider } from "./provider.ts";
+
+const off: BrowserCapabilityFlag = { supported: false, verified: false, source: "static", note: "未配置浏览器服务" };
+
+export function noneCapabilities(): BrowserCapabilities {
+  const flags = Object.fromEntries(BROWSER_CAPABILITY_KEYS.map((k) => [k, { ...off }])) as Record<
+    (typeof BROWSER_CAPABILITY_KEYS)[number],
+    BrowserCapabilityFlag
+  >;
+  return { ...flags, upstreamVersion: null, probedAt: null };
+}
+
+const unavailable = () => Promise.reject(new BrowserError("unavailable", "未配置浏览器服务"));
+
+/**
+ * 默认实现:未配置浏览器服务。所有动作返回 unavailable,能力全部 false;
+ * 业务侧据此在界面标注"浏览器不可用",不回退到其他浏览器。
+ */
+export function createNoneBrowserProvider(): BrowserProvider {
+  return {
+    kind: "none",
+    async health(): Promise<BrowserHealth> {
+      return { status: "disabled", kind: "none", detail: {}, checkedAt: new Date().toISOString() };
+    },
+    async capabilities() {
+      return noneCapabilities();
+    },
+    openSession: unavailable,
+    closeSession: unavailable,
+    async listSessions() {
+      return [];
+    },
+    navigate: unavailable,
+    snapshot: unavailable,
+    screenshot: unavailable,
+    click: unavailable,
+    type: unavailable,
+    extract: unavailable,
+    waitForDownload: unavailable,
+    acquireControl: unavailable,
+    releaseControl: unavailable,
+  };
+}