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>

src/get-url.ts

@@ -49,22 +49,34 @@ export default function getURL(
     );
   }
 
-  if (os === 'Windows') {
+  if (os === 'darwin') {
     return assetURLs(
       assetBases.flatMap(assetBase => [
-        `${assetBase}Windows-${arch}.zip`,
-        `${assetBase}windows-${lowerArch(arch)}.zip`
+        `${assetBase}darwin-${arch}.tar.gz`,
+        `${assetBase}darwin-${arch}.pkg`
       ])
     );
   }
 
-  if (os === 'Linux') {
+  if (os === 'Windows' || os === 'windows') {
+    const assetPatterns =
+      os === 'windows'
+        ? [`windows-${lowerArch(arch)}.zip`, `Windows-${arch}.zip`]
+        : [`Windows-${arch}.zip`, `windows-${lowerArch(arch)}.zip`];
+
     return assetURLs(
-      assetBases.flatMap(assetBase => [
-        `${assetBase}Linux-${arch}.tar.gz`,
-        `${assetBase}Linux_${arch}.tar.gz`,
-        `${assetBase}linux-${lowerArch(arch)}.tar.gz`
-      ])
+      assetBases.flatMap(assetBase => assetPatterns.map(asset => `${assetBase}${asset}`))
+    );
+  }
+
+  if (os === 'Linux' || os === 'linux') {
+    const assetPatterns =
+      os === 'linux'
+        ? [`linux-${lowerArch(arch)}.tar.gz`, `Linux-${arch}.tar.gz`, `Linux_${arch}.tar.gz`]
+        : [`Linux-${arch}.tar.gz`, `Linux_${arch}.tar.gz`, `linux-${lowerArch(arch)}.tar.gz`];
+
+    return assetURLs(
+      assetBases.flatMap(assetBase => assetPatterns.map(asset => `${assetBase}${asset}`))
     );
   }