fix: Hugo package naming fix (#688)

## Summary

Rebases the Hugo package naming fix from #609 on top of the current
`main` branch, including the installer flow added in #687.

- Derive Hugo release asset OS and architecture naming conventions from
the requested Hugo version.
- Apply those conventions when selecting OS and architecture segments,
including the 0.102.x macOS universal boundary, 0.103+ downcased OS
names, Windows zip assets, and Linux ARM assets.
- Add table-driven tests for pre-0.102, 0.102.x, and 0.103+ naming
behavior, plus URL coverage for the corrected release asset names.

## Changes

- Add `getConventions` to centralize version-based release asset naming
decisions.
- Update `getOS` and `getArch` to use convention flags for macOS,
lower-case OS names, standardized architecture names, and the Windows
ARM support boundary.
- Update `getURL` to generate candidate URLs for downcased Windows and
Linux assets, and for darwin universal archives.
- Wire convention detection into `installer` before generating candidate
Hugo release asset URLs.
- Expand unit coverage for OS, architecture, convention, and URL
behavior.

## Checklist

- [x] I have read the latest README and followed the instructions.
- [x] I have added or updated tests for behavior changes.
- [x] README.md and action.yml updates are not needed because inputs and
action metadata are unchanged.
- [x] I have run the relevant verification commands.

## References

- Rebased follow-up for
https://github.com/peaceiris/actions-hugo/pull/609
- References https://github.com/peaceiris/actions-hugo/issues/605 and
https://github.com/peaceiris/actions-hugo/issues/608
- Based on `main` after
https://github.com/peaceiris/actions-hugo/pull/687

## Verification

- [x] `RUNNER_TEMP=/private/tmp npm run all`
- [ ] `npm run build` was not run because this branch does not update
bundled output and current `main` removed `lib/index.js`.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Version-aware conventions control OS and architecture naming,
including macOS universal asset support and expanded darwin/macOS
patterns.

* **Refactor**
* Conventions centralized and applied across installer and URL
generation; OS/arch inputs accept varied casing and naming variants.

* **Tests**
* Expanded, data-driven parameterized tests for conventions, OS/arch
mappings, URL variants, and error cases.
* Replaced network stubs with deterministic fetch-mock helpers for test
isolation.

[![Review Change
Stack](https://storage.googleapis.com/coderabbit_public_assets/review-stack-in-coderabbit-ui.svg)](https://app.coderabbit.ai/change-stack/peaceiris/actions-hugo/pull/688)
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Michael T Lombardi <michael.t.lombardi@gmail.com>
Co-authored-by: codefactor-io <support@codefactor.io>
Co-authored-by: Codex <noreply@openai.com>

__tests__/get-url.test.ts

@@ -49,6 +49,32 @@ describe('getURL()', () => {
     ]);
   });
 
+  test('get URLs to macOS 0.102 universal assets', () => {
+    const baseURL = 'https://github.com/gohugoio/hugo/releases/download/v0.102.0';
+    expect(getURL('macOS', 'universal', 'false', '0.102.0')).toEqual([
+      `${baseURL}/hugo_0.102.0_macOS-universal.tar.gz`,
+      `${baseURL}/hugo_0.102.0_macOS-universal.zip`,
+      `${baseURL}/hugo_0.102.0_macOS-all.tar.gz`,
+      `${baseURL}/hugo_0.102.0_darwin-universal.tar.gz`,
+      `${baseURL}/hugo_0.102.0_darwin-universal.pkg`,
+      `${baseURL}/hugo_v0.102.0_macOS-universal.tar.gz`,
+      `${baseURL}/hugo_v0.102.0_macOS-universal.zip`,
+      `${baseURL}/hugo_v0.102.0_macOS-all.tar.gz`,
+      `${baseURL}/hugo_v0.102.0_darwin-universal.tar.gz`,
+      `${baseURL}/hugo_v0.102.0_darwin-universal.pkg`
+    ]);
+  });
+
+  test('get URLs to darwin assets', () => {
+    const baseURL = 'https://github.com/gohugoio/hugo/releases/download/v0.103.0';
+    expect(getURL('darwin', 'universal', 'false', '0.103.0')).toEqual([
+      `${baseURL}/hugo_0.103.0_darwin-universal.tar.gz`,
+      `${baseURL}/hugo_0.103.0_darwin-universal.pkg`,
+      `${baseURL}/hugo_v0.103.0_darwin-universal.tar.gz`,
+      `${baseURL}/hugo_v0.103.0_darwin-universal.pkg`
+    ]);
+  });
+
   test('get URLs to legacy macOS assets', () => {
     const baseURL = 'https://github.com/gohugoio/hugo/releases/download/v0.20.2';
     expect(getURL('macOS', '64bit', 'false', '0.20.2')).toEqual([
@@ -81,6 +107,16 @@ describe('getURL()', () => {
     ]);
   });
 
+  test('get URLs to downcased Windows assets', () => {
+    const baseURL = 'https://github.com/gohugoio/hugo/releases/download/v0.103.0';
+    expect(getURL('windows', 'amd64', 'false', '0.103.0')).toEqual([
+      `${baseURL}/hugo_0.103.0_windows-amd64.zip`,
+      `${baseURL}/hugo_0.103.0_Windows-amd64.zip`,
+      `${baseURL}/hugo_v0.103.0_windows-amd64.zip`,
+      `${baseURL}/hugo_v0.103.0_Windows-amd64.zip`
+    ]);
+  });
+
   test('get URLs to legacy Windows assets', () => {
     const baseURL = 'https://github.com/gohugoio/hugo/releases/download/v0.20.3';
     expect(getURL('Windows', '64bit', 'false', '0.20.3')).toEqual([
@@ -91,6 +127,18 @@ describe('getURL()', () => {
     ]);
   });
 
+  test('get URLs to downcased Linux assets', () => {
+    const baseURL = 'https://github.com/gohugoio/hugo/releases/download/v0.103.0';
+    expect(getURL('linux', 'arm', 'false', '0.103.0')).toEqual([
+      `${baseURL}/hugo_0.103.0_linux-arm.tar.gz`,
+      `${baseURL}/hugo_0.103.0_Linux-arm.tar.gz`,
+      `${baseURL}/hugo_0.103.0_Linux_arm.tar.gz`,
+      `${baseURL}/hugo_v0.103.0_linux-arm.tar.gz`,
+      `${baseURL}/hugo_v0.103.0_Linux-arm.tar.gz`,
+      `${baseURL}/hugo_v0.103.0_Linux_arm.tar.gz`
+    ]);
+  });
+
   test('get a fallback URL to an unknown OS asset', () => {
     const baseURL = 'https://github.com/gohugoio/hugo/releases/download/v0.58.2';
     expect(getURL('MyOS', '64bit', 'false', '0.58.2')).toEqual([