fix(sandbox): address PR #250 review — SSRF guard, eviction safety, cleanup (#243)

Security:
- stash_page: reject path-traversal / percent-encoded srcs before the authed
  loopback fetch (resolveInternalFilePath), closing an SSRF/exfiltration hole
  where a crafted node.attrs.src could read an arbitrary internal GET endpoint
  into the anonymous sandbox.

Stability:
- stash_page: revert + recount mirrors FIFO-evicted by a later put in the same
  stash (no dangling sandbox refs, honest images.mirrored/failed); free image
  blobs if the final document put throws.
- Reject/clamp non-positive SANDBOX_TTL_MS to the 1h default (warn once).
- Log mirror failures unconditionally (console.warn, no blob bodies).

Cleanup / architecture:
- Remove dead expiresAt from SandboxPutResult.
- Centralize the /api/sb route in SANDBOX_ROUTE_SEGMENT/SANDBOX_API_PATH and
  move URL composition into SandboxStore.putAndLink; drop the duplicated sink
  closures and the now-unused EnvironmentService injection from McpService and
  AiChatToolsService.
- Un-export isInternalFileUrl; document the process-local (instance-bound)
  sandbox limitation in the tool description and .env.example.

Docs/tests:
- README/README.ru: 38 -> 39 tools + stash_page entry.
- Add traversal/normalize/recursion unit tests, stash self-eviction +
  doc-put-throw + empty/octet-stream mock tests, controller If-None-Match
  (wildcard/weak/list) + Cache-Control tests, and SANDBOX_TTL_MS validation
  tests. Regenerate packages/mcp/build.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/server/src/integrations/environment/environment.service.spec.ts

@@ -14,4 +14,30 @@ describe('EnvironmentService', () => {
   it('should be defined', () => {
     expect(service).toBeDefined();
   });
+
+  describe('getSandboxTtlMs', () => {
+    // ConfigService stub: get(key, def) returns the configured value for the key
+    // (falling back to def), matching the @nestjs/config contract the service
+    // calls with (key, default).
+    const build = (sandboxTtl?: string) =>
+      new EnvironmentService({
+        get: (key: string, def?: string) =>
+          key === 'SANDBOX_TTL_MS' ? (sandboxTtl ?? def) : def,
+      } as any);
+
+    it.each(['0', '-5', 'abc'])(
+      'falls back to the 3600000 default for invalid value %s',
+      (value) => {
+        expect(build(value).getSandboxTtlMs()).toBe(3_600_000);
+      },
+    );
+
+    it('returns the parsed value for a valid positive integer', () => {
+      expect(build('120000').getSandboxTtlMs()).toBe(120_000);
+    });
+
+    it('uses the 3600000 default when SANDBOX_TTL_MS is unset', () => {
+      expect(build(undefined).getSandboxTtlMs()).toBe(3_600_000);
+    });
+  });
 });