refactor: move act under internal

The runner is an application, not a library. `act/model` and
`act/exprparser` were the last packages anything outside this repository
consumed and they now live in actionslib, so nothing needs the rest of
`act` to be importable, and keeping it importable invites the coupling
that was just removed.

Import paths only, the files are unchanged.

Assisted-by: Codet:GPT-5.1-Codex

internal/act/runner/testdata/uses-composite/composite_action/action.yml

@@ -0,0 +1,97 @@
+---
+name: "Test Composite Action"
+description: "Test action uses composite"
+
+inputs:
+  test_input_required:
+    description: "Required input"
+    required: true
+  test_input_optional:
+    description: "optional defaulted input"
+    required: false
+    default: "test_input_optional_value"
+  test_input_optional_with_default_overriden:
+    description: "optional defaulted input"
+    required: false
+    default: "test_input_optional_value"
+  test_input_required_with_default:
+    description: "Required with default, due to an old bug of github actions this is allowed"
+    required: true
+    default: "test_input_optional_value"
+  test_input_required_with_default_overriden:
+    description: "Required with default, due to an old bug of github actions this is allowed"
+    required: true
+    default: "test_input_optional_value"
+  secret_input:
+    description: test pass a secret as input
+outputs:
+  test_output:
+    description: "Output value to pass up"
+    value: ${{ steps.output.outputs.test_output }}
+  secret_output:
+    description: test pass a secret as output
+    value: ${{ format('{0}/{1}', inputs.secret_input, env.secret_input) }}
+
+runs:
+  using: "composite"
+  steps:
+    - name: echo inputs
+      run: |
+        echo "#####################################"
+        echo "Inputs:"
+        echo "---"
+        echo "test_input_required=${{ inputs.test_input_required }}"
+        echo "test_input_optional=${{ inputs.test_input_optional }}"
+        echo "test_input_optional_with_default_overriden=${{ inputs.test_input_optional_with_default_overriden }}"
+        echo "test_input_required_with_default=${{ inputs.test_input_required_with_default }}"
+        echo "test_input_required_with_default_overriden=${{ inputs.test_input_required_with_default_overriden }}"
+        echo "---"
+      shell: bash
+
+    # Let's test the inputs
+    - run: |
+        if [ "${{ inputs.test_input_required }}" != "test_input_required_value" ]; then
+          exit 1
+        fi
+      shell: bash
+
+    - run: |
+        if [ "${{ inputs.test_input_optional }}" != "test_input_optional_value" ]; then
+          exit 1
+        fi
+      shell: bash
+
+    - run: |
+        if [ "${{ inputs.test_input_optional_with_default_overriden }}" != "test_input_optional_with_default_overriden" ]; then
+          exit 1
+        fi
+      shell: bash
+
+    - run: |
+        if [ "${{ inputs.test_input_required_with_default }}" != "test_input_optional_value" ]; then
+          exit 1
+        fi
+      shell: bash
+
+    - run: |
+        if [ "${{ inputs.test_input_required_with_default_overriden }}" != "test_input_required_with_default_overriden" ]; then
+          exit 1
+        fi
+      shell: bash
+
+    - run: |
+        if [ -z "$GITHUB_ACTION_PATH" ]; then
+          exit 1
+        fi
+        if [ -z "${{ github.action_path }}" ]; then
+          exit 2
+        fi
+      shell: bash
+
+    # Let's send up an output to test
+    - run: echo "::set-output name=test_output::test_output_value"
+      id: output
+      shell: bash
+    - run: echo "COMPOSITE_ACTION_ENV_OUTPUT=my test value" >> $GITHUB_ENV
+      shell: bash
+

internal/act/runner/testdata/uses-composite/push.yml

@@ -0,0 +1,44 @@
+name: uses-docker-url
+on: push
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: ./uses-composite/composite_action
+      id: composite
+      with:
+        test_input_required: 'test_input_required_value'
+        test_input_optional: 'test_input_optional_value'
+        test_input_optional_with_default_overriden: 'test_input_optional_with_default_overriden'
+        test_input_required_with_default: 'test_input_optional_value'
+        test_input_required_with_default_overriden: 'test_input_required_with_default_overriden'
+        secret_input: ${{secrets.test_input_optional || 'NO SUCH SECRET'}}
+      env:
+        secret_input: ${{secrets.test_input_optional || 'NO SUCH SECRET'}}
+    - if: steps.composite.outputs.test_output != 'test_output_value'
+      run: |
+        echo "steps.composite.outputs.test_output=${{ steps.composite.outputs.test_output }}"
+        exit 1
+    - run: |
+        echo "steps.composite.outputs.secret_output=${{ steps.composite.outputs.secret_output }}"
+        [[ "${{steps.composite.outputs.secret_output == format('{0}/{0}', secrets.test_input_optional || 'NO SUCH SECRET')}}" = "true" ]] || exit 1
+      shell: bash
+    - run: |
+        echo "steps.composite.outputs.secret_output=$COMPOSITE_ACTION_ENV_OUTPUT"
+        [[ "${{env.COMPOSITE_ACTION_ENV_OUTPUT == 'my test value' }}" = "true" ]] || exit 1
+      shell: bash
+
+    # Now test again with default values
+    - uses: ./uses-composite/composite_action
+      id: composite2
+      with:
+        test_input_required: 'test_input_required_value'
+        test_input_optional_with_default_overriden: 'test_input_optional_with_default_overriden'
+        test_input_required_with_default_overriden: 'test_input_required_with_default_overriden'
+
+    - if: steps.composite2.outputs.test_output != 'test_output_value'
+      run: |
+        echo "steps.composite.outputs.test_output=${{ steps.composite2.outputs.test_output }}"
+        exit 1