gha cleanups (#6275)

# Description of Changes

Adds all pre commit PR checks under single file with job validator to
have a true "required" run step "all-checks-passed" check
Moves all GHAs into workflow helper function calls 

Note if: always() overrides the default skip-on-needs-failure, "Needs"
is added to ensure the validation runs at end of all other tasks

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have run `task check` to verify linters, typechecks, and tests
pass
- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#7-testing)
for more details.

.github/workflows/tauri-build.yml

@@ -1,6 +1,17 @@
 name: Build Tauri Applications
 
+# Multi-OS Tauri desktop bundle build matrix (Windows / macOS arm+intel /
+# Linux). Called from build.yml on PRs that touch desktop sources (gated
+# via the `tauri` filter in .github/config/.files.yaml). Also runnable
+# on demand via workflow_dispatch with a per-platform selector.
 on:
+  workflow_call:
+    inputs:
+      platform:
+        description: "Platform to build (windows, macos, linux, or all)."
+        required: false
+        type: string
+        default: "all"
   workflow_dispatch:
     inputs:
       platform:
@@ -13,17 +24,6 @@ on:
           - windows
           - macos
           - linux
-  pull_request:
-    branches: [main]
-    types: [opened, reopened, synchronize, ready_for_review]
-    paths:
-      - "frontend/src-tauri/**"
-      - "frontend/src/desktop/**"
-      - "frontend/tsconfig.desktop.json"
-      - "frontend/package.json"
-      - "frontend/package-lock.json"
-      - "frontend/vite.config.ts"
-      - ".github/workflows/tauri-build.yml"
 
 permissions:
   contents: read
@@ -45,20 +45,15 @@ jobs:
         id: set-matrix
         env:
           APPLE_CERTIFICATE: ${{ secrets.APPLE_CERTIFICATE }}
+          PLATFORM: ${{ inputs.platform }}
         run: |
           WINDOWS='{"platform":"windows-latest","args":"--target x86_64-pc-windows-msvc","name":"windows-x86_64"}'
           MACOS_ARM='{"platform":"macos-15","args":"--target aarch64-apple-darwin","name":"macos-aarch64"}'
           MACOS_INTEL='{"platform":"macos-15-intel","args":"--target x86_64-apple-darwin","name":"macos-x86_64"}'
           LINUX='{"platform":"ubuntu-22.04","args":"","name":"linux-x86_64"}'
 
-          # Resolve requested platform (non-dispatch events always build all)
-          if [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
-            PLATFORM="${{ github.event.inputs.platform }}"
-          else
-            PLATFORM="all"
-          fi
-
-          # Build candidate list
+          # Resolve requested platform — populated by either workflow_dispatch
+          # or workflow_call inputs; both paths default to "all".
           case "$PLATFORM" in
             windows) ENTRIES=("$WINDOWS") ;;
             macos)   ENTRIES=("$MACOS_ARM" "$MACOS_INTEL") ;;