fix(ci): Plumb node-version through repomix composite action

The composite action hard-coded `setup-node` to Node 24, so the
`test-action.yml` matrix `[22, 24, 26]` silently ran every job under
Node 24 — the 22 and 26 cells did not actually exercise those Node
versions.

Add a `node-version` input to the action (default `"24"` to preserve
current behavior for downstream consumers) and pass `${{
matrix.node-version }}` from each `test-action.yml` invocation so the
matrix tests what its name implies.

.github/actions/repomix/action.yml

@@ -38,6 +38,10 @@ inputs:
     description: "Version (or tag) of the npm package to install – defaults to latest"
     required: false
     default: "latest"
+  node-version:
+    description: "Node.js version to use (defaults to 24)"
+    required: false
+    default: "24"
 
 runs:
   using: "composite"
@@ -45,7 +49,7 @@ runs:
     - name: Setup Node.js
       uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
       with:
-        node-version: "24"
+        node-version: ${{ inputs.node-version }}
     - name: Install project dependencies
       shell: bash
       run: |

.github/workflows/test-action.yml

@@ -32,12 +32,14 @@ jobs:
         if: matrix['test-case'] == 'minimal'
         uses: ./.github/actions/repomix
         with:
+          node-version: ${{ matrix.node-version }}
           output: "repomix-minimal-output.txt"
 
       - name: Run Repomix Action (Basic)
         if: matrix['test-case'] == 'basic'
         uses: ./.github/actions/repomix
         with:
+          node-version: ${{ matrix.node-version }}
           directories: "src"
           include: "**/*.ts"
           output: "repomix-basic-output.txt"
@@ -47,6 +49,7 @@ jobs:
         if: matrix['test-case'] == 'full'
         uses: ./.github/actions/repomix
         with:
+          node-version: ${{ matrix.node-version }}
           directories: "src tests"
           include: "**/*.ts,**/*.md"
           ignore: "**/*.test.ts"