refactor: inline PHP detection into php-laravel-phpunit

Replace language-version-detect dependency with inline version detection
for the Laravel PHPUnit testing action.

Detection logic checks (in priority order):
- .tool-versions file (php key)
- Dockerfile (FROM php: image)
- devcontainer.json (php: image)
- .php-version file
- composer.json (require.php or config.platform.php fields)

Implementation details:
- POSIX sh compliant with `set -eu`
- Validates version format: X.Y or X.Y.Z
- Normalizes versions: strips 'v' prefix, whitespace, line endings
- Uses `sed -E` for portable extended regex (Dockerfile/devcontainer)
- Uses basic sed for composer.json (POSIX-compatible backslash escapes)
- Conditional jq usage with diagnostic messages
- Maintains output contract (detected-version)

Changes:
- php-laravel-phpunit: ~115 lines of inline detection + jq diagnostics
- README regenerated with action-docs

Benefits:
- Eliminates external dependency for PHP version detection
- Reduces action initialization time
- Improved debugging (diagnostic messages, all logic in one file)
- Consistent with go-build, csharp, and python-lint-fix pattern

php-laravel-phpunit/action.yml

@@ -60,10 +60,118 @@ runs:
 
     - name: Detect PHP Version
       id: php-version
-      uses: ivuorinen/actions/language-version-detect@0fa9a68f07a1260b321f814202658a6089a43d42
-      with:
-        language: 'php'
-        default-version: ${{ inputs.php-version }}
+      shell: sh
+      env:
+        DEFAULT_VERSION: "${{ inputs.php-version || '8.4' }}"
+      run: |
+        set -eu
+
+        # Function to validate version format
+        validate_version() {
+          version=$1
+          case "$version" in
+            [0-9]*.[0-9]* | [0-9]*.[0-9]*.[0-9]*)
+              return 0
+              ;;
+            *)
+              return 1
+              ;;
+          esac
+        }
+
+        # Function to clean version string
+        clean_version() {
+          printf '%s' "$1" | sed 's/^[vV]//' | tr -d ' \n\r'
+        }
+
+        detected_version=""
+
+        # Parse .tool-versions file
+        if [ -f .tool-versions ]; then
+          echo "Checking .tool-versions for php..." >&2
+          version=$(awk '/^php[[:space:]]/ {gsub(/#.*/, ""); print $2; exit}' .tool-versions 2>/dev/null || echo "")
+          if [ -n "$version" ]; then
+            version=$(clean_version "$version")
+            if validate_version "$version"; then
+              echo "Found PHP version in .tool-versions: $version" >&2
+              detected_version="$version"
+            fi
+          fi
+        fi
+
+        # Parse Dockerfile
+        if [ -z "$detected_version" ] && [ -f Dockerfile ]; then
+          echo "Checking Dockerfile for php..." >&2
+          version=$(grep -iF "FROM" Dockerfile | grep -F "php:" | head -1 | \
+            sed -n -E "s/.*php:([0-9]+(\.[0-9]+)*)(-[^:]*)?.*/\1/p" || echo "")
+          if [ -n "$version" ]; then
+            version=$(clean_version "$version")
+            if validate_version "$version"; then
+              echo "Found PHP version in Dockerfile: $version" >&2
+              detected_version="$version"
+            fi
+          fi
+        fi
+
+        # Parse devcontainer.json
+        if [ -z "$detected_version" ] && [ -f .devcontainer/devcontainer.json ]; then
+          echo "Checking devcontainer.json for php..." >&2
+          if command -v jq >/dev/null 2>&1; then
+            version=$(jq -r '.image // empty' .devcontainer/devcontainer.json 2>/dev/null | sed -n -E "s/.*php:([0-9]+(\.[0-9]+)*)(-[^:]*)?.*/\1/p" || echo "")
+            if [ -n "$version" ]; then
+              version=$(clean_version "$version")
+              if validate_version "$version"; then
+                echo "Found PHP version in devcontainer: $version" >&2
+                detected_version="$version"
+              fi
+            fi
+          else
+            echo "jq not found; skipping devcontainer.json parsing" >&2
+          fi
+        fi
+
+        # Parse .php-version file
+        if [ -z "$detected_version" ] && [ -f .php-version ]; then
+          echo "Checking .php-version..." >&2
+          version=$(tr -d '\r' < .php-version | head -1)
+          if [ -n "$version" ]; then
+            version=$(clean_version "$version")
+            if validate_version "$version"; then
+              echo "Found PHP version in .php-version: $version" >&2
+              detected_version="$version"
+            fi
+          fi
+        fi
+
+        # Parse composer.json
+        if [ -z "$detected_version" ] && [ -f composer.json ]; then
+          echo "Checking composer.json..." >&2
+          if command -v jq >/dev/null 2>&1; then
+            version=$(jq -r '.require.php // empty' composer.json 2>/dev/null | sed -n 's/[^0-9]*\\([0-9]\\+\\.[0-9]\\+\\(\\.[0-9]\\+\\)\\?\\).*/\\1/p')
+            if [ -z "$version" ]; then
+              version=$(jq -r '.config.platform.php // empty' composer.json 2>/dev/null | sed -n 's/[^0-9]*\\([0-9]\\+\\.[0-9]\\+\\(\\.[0-9]\\+\\)\\?\\).*/\\1/p')
+            fi
+            if [ -n "$version" ]; then
+              version=$(clean_version "$version")
+              if validate_version "$version"; then
+                echo "Found PHP version in composer.json: $version" >&2
+                detected_version="$version"
+              fi
+            fi
+          else
+            echo "jq not found; skipping composer.json parsing" >&2
+          fi
+        fi
+
+        # Use default version if nothing detected
+        if [ -z "$detected_version" ]; then
+          detected_version="$DEFAULT_VERSION"
+          echo "Using default PHP version: $detected_version" >&2
+        fi
+
+        # Set output
+        printf 'detected-version=%s\n' "$detected_version" >> "$GITHUB_OUTPUT"
+        echo "Final detected PHP version: $detected_version" >&2
 
     - uses: shivammathur/setup-php@bf6b4fbd49ca58e4608c9c89fba0b8d90bd2a39f # 2.35.5
       id: setup-php