feat: backport cache read-denied + ACTIONS_CACHE_MODE handling (5.2.0)

Backport of the read-denied and ACTIONS_CACHE_MODE cache-mode gating from
the ESM v6.2.0 line (#2447) to the CommonJS v5 line, released as 5.2.0.
Mirrors the earlier write-denied backport (#2435, 5.1.0).

- Detect the `cache read denied:` prefix on download failures (v2 twirp
  path and v1 `_apis/artifactcache` path) and surface it as a core.warning
  without failing the run.
- Honor ACTIONS_CACHE_MODE: skip restore when the effective cache-mode does
  not permit reads (none, write-only) and skip save when it does not permit
  writes (none, read), logging a single non-fatal core.info line. Unset or
  unrecognized modes are unchanged.
- Add read-denied and cache-mode tests; bump to 5.2.0 with RELEASES entry.

Co-authored-by: Copilot App <[email protected]>
Copilot-Session: e96deec1-716e-4e14-acdf-a230139420a2

packages/cache/__tests__/cacheHttpClient.test.ts

@@ -1,8 +1,10 @@
-import {downloadCache} from '../src/internal/cacheHttpClient'
+import {downloadCache, getCacheEntry} from '../src/internal/cacheHttpClient'
 import {getCacheVersion} from '../src/internal/cacheUtils'
 import {CompressionMethod} from '../src/internal/constants'
 import * as downloadUtils from '../src/internal/downloadUtils'
+import * as requestUtils from '../src/internal/requestUtils'
 import {DownloadOptions, getDownloadOptions} from '../src/options'
+import {HttpClientError} from '@actions/http-client'
 
 jest.mock('../src/internal/downloadUtils')
 
@@ -57,6 +59,37 @@ test('getCacheVersion with enableCrossOsArchive as false returns version on wind
   }
 })
 
+test('getCacheEntry throws a generic status-code error for non-read-denied failures', async () => {
+  // Regression: a non read-denied failure must NOT leak the server's body
+  // message; it should surface the generic status-code error.
+  jest.spyOn(requestUtils, 'retryTypedResponse').mockResolvedValue({
+    statusCode: 403,
+    result: null,
+    headers: {},
+    error: new HttpClientError('some other server detail', 403)
+  })
+
+  await expect(getCacheEntry(['key'], ['node_modules'])).rejects.toThrow(
+    'Cache service responded with 403'
+  )
+})
+
+test('getCacheEntry surfaces the body message for a cache read denial', async () => {
+  jest.spyOn(requestUtils, 'retryTypedResponse').mockResolvedValue({
+    statusCode: 403,
+    result: null,
+    headers: {},
+    error: new HttpClientError(
+      'cache read denied: token has no readable scopes',
+      403
+    )
+  })
+
+  await expect(getCacheEntry(['key'], ['node_modules'])).rejects.toThrow(
+    'cache read denied: token has no readable scopes'
+  )
+})
+
 test('downloadCache uses http-client for non-Azure URLs', async () => {
   const downloadCacheHttpClientMock = jest.spyOn(
     downloadUtils,