ci: add path-based filtering to skip unnecessary builds (#319)

- unified-pipeline.yml: replace blanket .github/workflows/** glob with
  specific .github/workflows/unified-pipeline.yml in both web and python
  filters, so editing nightly.yml or release.yml no longer triggers the
  full lint/test/build matrix
- distro-test-matrix.yml: add paths filter at workflow trigger level so
  the 4-container distro matrix only runs when installer, scripts,
  packaging, or version files change (previously ran on every push/PR
  including doc-only and web-only changes)

Saves CI minutes on documentation, website, and unrelated workflow edits.

.github/workflows/distro-test-matrix.yml

@@ -3,8 +3,24 @@ name: Distro Test Matrix
 on:
   push:
     branches: [ main, master ]
+    paths:
+      - 'install.sh'
+      - 'scripts/**'
+      - 'pyproject.toml'
+      - 'setup.py'
+      - 'setup.cfg'
+      - 'src/vocalinux/version.py'
+      - '.github/workflows/distro-test-matrix.yml'
   pull_request:
     branches: [ main, master ]
+    paths:
+      - 'install.sh'
+      - 'scripts/**'
+      - 'pyproject.toml'
+      - 'setup.py'
+      - 'setup.cfg'
+      - 'src/vocalinux/version.py'
+      - '.github/workflows/distro-test-matrix.yml'
   workflow_dispatch:
 
 jobs:

.github/workflows/unified-pipeline.yml

@@ -32,7 +32,7 @@ jobs:
           filters: |
             web:
               - 'web/**'
-              - '.github/workflows/**'
+              - '.github/workflows/unified-pipeline.yml'
             python:
               - 'src/**'
               - 'tests/**'
@@ -42,7 +42,7 @@ jobs:
               - 'requirements*.txt'
               - 'Makefile'
               - '.pre-commit-config.yaml'
-              - '.github/workflows/**'
+              - '.github/workflows/unified-pipeline.yml'
       - name: Check if website should deploy
         id: deploy_check
         env: