test(sandbox): address PR #250 round-4 review — SSRF accept-path tests, MCP structuredContent (#243)

Mandatory (test-coverage):
- internal-file-urls.test: pin the SSRF/traversal ACCEPT path of
  resolveInternalFilePath (the sole guard for content-controlled `src`): an
  absolute/protocol-relative URL has its foreign host dropped and only an
  /api/files/ pathname survives (http://evil.com/api/files/x/y.png -> /files/x/y.png),
  while a host-dropped path that escapes /api/files/ (https://evil.com/api/auth/whoami)
  or a backslash-traversal (/api/files\..\auth\whoami) is rejected. Locks the
  behavior so a future prefix-only refactor cannot silently open a bypass.

Suggestions:
- index.ts: the stash_page MCP tool now returns structuredContent
  { uri, sha256, size, images } alongside the resource_link, so the MCP output
  matches the documented shape (clients get the blob's sha256/ETag and the
  mirror counts, not just the link). No outputSchema registered. Rebuilt build/.
- new stash-page-mcp-result.test: server round-trip via InMemoryTransport asserts
  both the resource_link and the structuredContent mirror.
- internal-file-urls.test: cover the new URL parse-failure catch branch
  (http://[ -> "Invalid internal file src").
- environment.service.spec: assert getPositiveIntEnv warns once per key and
  independently across keys (the invalidPositiveIntWarned dedup).

Tests: packages/mcp 383 pass; apps/server sandbox/environment/mcp 235 pass.

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

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

@@ -94,6 +94,46 @@ describe('EnvironmentService', () => {
     });
   });
 
+  // getPositiveIntEnv keeps a one-shot `invalidPositiveIntWarned` set so a bad
+  // value is logged ONCE per key (not on every getter call, which the sandbox
+  // hits per-put). These tests pin that dedup so a regression to per-call logging
+  // would fail loudly.
+  describe('invalid-value warn dedup', () => {
+    it('warns only once per key across repeated getter calls', () => {
+      const service = new EnvironmentService({
+        get: (k: string, d?: string) =>
+          k === 'SANDBOX_MAX_TOTAL_BYTES' ? '-5' : d,
+      } as any);
+      const warnSpy = jest
+        .spyOn((service as any).logger, 'warn')
+        .mockImplementation(() => undefined);
+
+      service.getSandboxMaxTotalBytes();
+      service.getSandboxMaxTotalBytes();
+
+      expect(warnSpy).toHaveBeenCalledTimes(1);
+    });
+
+    it('warns independently per key (dedup is per-key, not global)', () => {
+      // Two DIFFERENT SANDBOX_* keys are both invalid -> each warns once, so two
+      // warns total. This proves the dedup set is keyed, not a single global flag.
+      const service = new EnvironmentService({
+        get: (k: string, d?: string) =>
+          k === 'SANDBOX_MAX_BYTES' || k === 'SANDBOX_MAX_TOTAL_BYTES'
+            ? '-5'
+            : d,
+      } as any);
+      const warnSpy = jest
+        .spyOn((service as any).logger, 'warn')
+        .mockImplementation(() => undefined);
+
+      service.getSandboxMaxBytes();
+      service.getSandboxMaxTotalBytes();
+
+      expect(warnSpy).toHaveBeenCalledTimes(2);
+    });
+  });
+
   describe('getSandboxPublicUrl', () => {
     // Stub that resolves BOTH keys the public-url logic consults.
     const build = (vals: { sandboxUrl?: string; appUrl?: string }) =>