Render configuration-cache status in the caching Job Summary (#989)

Render the configuration-cache restore-state in the caching Job Summary,
driven by the new `CacheReport.configurationCache` field produced by the
`gradle-actions-caching` provider.

## What's here

- `cache-service.ts`: add a `ConfigurationCacheStatus` type
(`not-active` / `restored` / `not-restored` / `restore-incomplete`) and
an optional `configurationCache` field on `CacheReport`.
- `caching-report.ts`: a `CONFIG_CACHE_COPY` map and a prominent status
line in `renderCachingReport`, beside the cleanup line. The `not-active`
case links to the `#cache-encryption-key` docs.

## Cross-repo dependency

The field is populated by gradle/actions-caching PR #75 ("Restore
configuration-cache support for simple builds"). This rendering compiles
independently (it uses this repo's own `CacheReport` type) and renders
nothing until the vendored `gradle-actions-caching` bundle is refreshed
from that branch — so this should land with/after the vendor refresh.

## Verification

`npm run check` clean; full Jest suite (366 tests) passes, including 3
new rendering tests.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

sources/test/jest/caching-report.test.ts

@@ -79,6 +79,39 @@ describe('renderCachingReport', () => {
         expect(md).toContain('<summary>Entries: 1 restored, 0 saved - Expand for more details</summary>')
     })
 
+    it('renders the configuration-cache status line inside the details', () => {
+        const report: CacheReport = {
+            status: 'enabled',
+            cleanup: 'enabled',
+            configurationCache: 'restored',
+            entries: [entry()]
+        }
+        const md = renderCachingReport(report, ENHANCED)
+
+        const detailsBody = md.slice(md.indexOf('</summary>'))
+        expect(detailsBody).toContain('Configuration cache state was restored from the cache.')
+    })
+
+    it('explains an inactive configuration cache with a link to the encryption key docs', () => {
+        const report: CacheReport = {
+            status: 'enabled',
+            cleanup: 'enabled',
+            configurationCache: 'not-active',
+            entries: [entry()]
+        }
+        const md = renderCachingReport(report, ENHANCED)
+
+        expect(md).toContain('Configuration cache state was not cached')
+        expect(md).toContain('#cache-encryption-key')
+    })
+
+    it('omits the configuration-cache line when the status is absent', () => {
+        const report: CacheReport = {status: 'enabled', cleanup: 'enabled', entries: [entry()]}
+        const md = renderCachingReport(report, ENHANCED)
+
+        expect(md).not.toContain('Configuration cache state')
+    })
+
     it('renders a compact disabled report with no note and no details', () => {
         const report: CacheReport = {status: 'disabled', entries: []}
         const md = renderCachingReport(report, undefined)