Verify JDK downloads with vendor checksums (#1167)

* Verify JDK downloads with vendor checksums

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

* Handle missing vendor checksum values

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

* Preserve checksum error during cleanup failure

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

* Validate checksum metadata value types

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

* Clarify checksum documentation

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

* Expand vendor checksum verification

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

* Accept SHA-256 or SHA-512 for JetBrains checksum sibling

JetBrains publishes a single, generically-named ".checksum" sibling
whose digest algorithm isn't disclosed by the filename. Older JBR 11
builds (e.g. jbrsdk_nomod-11_0_16-*-b2043.64.tar.gz) publish a SHA-256
digest there, while newer builds publish SHA-512. The JetBrains
installer previously assumed SHA-512 unconditionally, so verification
failed with "Malformed sha512 checksum metadata ... expected a
128-character hexadecimal digest" for those older builds, breaking the
jetbrains 11 e2e job on macOS and Windows.

fetchChecksum now accepts a list of candidate algorithms and infers
the actual algorithm from the returned digest's length, preferring the
strongest match. The JetBrains installer passes ['sha512', 'sha256'];
all other callers are unaffected since they already pass a single,
vendor-disclosed algorithm.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

* Use SapMachine archive checksum files

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

---------

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: a800a031-600e-4d28-b23e-be309555d38d

README.md

@@ -95,6 +95,14 @@ For more details,  see the full release notes on the [releases page](https://git
 
   - `show-download-progress`: Set to `true` to keep Maven artifact download and transfer progress in build logs. Default value: `false`. By default, the action adds `-ntp` (`--no-transfer-progress`) to `MAVEN_ARGS`. This input has no effect on non-Maven builds. See [Maven transfer progress](docs/advanced-usage.md#maven-transfer-progress-download-logs) for more details.
 
+### Download integrity verification
+
+When a selected distribution publishes an authoritative checksum for an archive, `setup-java` automatically verifies each downloaded JDK, JRE, or JMOD archive before extraction and caching. No input is required. Automatic checksum verification is currently available for `temurin`, `semeru`, `adopt`, `corretto`, `dragonwell`, `kona`, `sapmachine`, `graalvm`, `graalvm-community`, `zulu`, `oracle`, `oracle-openjdk`, `microsoft`, and `jetbrains`.
+
+Distributions or individual releases without an authoritative checksum continue to install normally, with the omission reported only in debug logs. Archives resolved directly from the runner tool cache are not downloaded again and therefore are not reverified.
+
+Checksums detect corrupted or unexpectedly modified downloads before they are persisted in the runner tool cache.
+
 ### Basic Configuration
 
 #### Eclipse Temurin