feat: add comprehensive unit tests for pipeline stages (#1701)

* feat: add comprehensive unit tests for pipeline stages

* fix: deps install in ci

* ci: use venv

* ci: run run_tests.sh

* fix: resolve circular import issues in pipeline tests

Update all test files to use lazy imports via importlib.import_module()
to avoid circular dependency errors. Fix mock_conversation fixture to
properly mock list.copy() method.

Changes:
- Use lazy import pattern in all test files
- Fix conftest.py fixture for conversation messages
- Add integration test file for full import tests
- Update documentation with known issues and workarounds

Tests now successfully avoid circular import errors while maintaining
full test coverage of pipeline stages.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* docs: add comprehensive testing summary

Document implementation details, challenges, solutions, and future
improvements for the pipeline unit test suite.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* refactor: rewrite unit tests to test actual pipeline stage code

Rewrote unit tests to properly test real stage implementations instead of
mock logic:

- Test actual BanSessionCheckStage with 7 test cases (100% coverage)
- Test actual RateLimit stage with 3 test cases (70% coverage)
- Test actual PipelineManager with 5 test cases
- Use lazy imports via import_module to avoid circular dependencies
- Import pipelinemgr first to ensure proper stage registration
- Use Query.model_construct() to bypass Pydantic validation in tests
- Remove obsolete pure unit tests that didn't test real code
- All 20 tests passing with 48% overall pipeline coverage

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* test: add unit tests for GroupRespondRuleCheckStage

Added comprehensive unit tests for resprule stage:

- Test person message skips rule check
- Test group message with no matching rules (INTERRUPT)
- Test group message with matching rule (CONTINUE)
- Test AtBotRule removes At component correctly
- Test AtBotRule when no At component present

Coverage: 100% on resprule.py and atbot.py
All 25 tests passing with 51% overall pipeline coverage

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* refactor: restructure tests to tests/unit_tests/pipeline

Reorganized test directory structure to support multiple test categories:

- Move tests/pipeline → tests/unit_tests/pipeline
- Rename .github/workflows/pipeline-tests.yml → run-tests.yml
- Update run_tests.sh to run all unit tests (not just pipeline)
- Update workflow to trigger on all pkg/** and tests/** changes
- Coverage now tracks entire pkg/ module instead of just pipeline

This structure allows for easy addition of more unit tests for other
modules in the future.

All 25 tests passing with 21% overall pkg coverage.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* ci: upload codecov report

* ci: codecov file

* ci: coverage.xml

---------

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/run-tests.yml

@@ -0,0 +1,71 @@
+name: Unit Tests
+
+on:
+  pull_request:
+    types: [opened, ready_for_review, synchronize]
+    paths:
+      - 'pkg/**'
+      - 'tests/**'
+      - '.github/workflows/run-tests.yml'
+      - 'pyproject.toml'
+      - 'run_tests.sh'
+  push:
+    branches:
+      - master
+      - develop
+    paths:
+      - 'pkg/**'
+      - 'tests/**'
+      - '.github/workflows/run-tests.yml'
+      - 'pyproject.toml'
+      - 'run_tests.sh'
+
+jobs:
+  test:
+    name: Run Unit Tests
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ['3.10', '3.11', '3.12']
+      fail-fast: false
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install uv
+        run: |
+          curl -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.cargo/bin" >> $GITHUB_PATH
+
+      - name: Install dependencies
+        run: |
+          uv sync --dev
+
+      - name: Run unit tests
+        run: |
+          bash run_tests.sh
+
+      - name: Upload coverage to Codecov
+        if: matrix.python-version == '3.12'
+        uses: codecov/codecov-action@v5
+        with:
+          files: ./coverage.xml
+          flags: unit-tests
+          name: unit-tests-coverage
+          fail_ci_if_error: false
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+
+      - name: Test Summary
+        if: always()
+        run: |
+          echo "## Unit Tests Results" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "Python Version: ${{ matrix.python-version }}" >> $GITHUB_STEP_SUMMARY
+          echo "Test Status: ${{ job.status }}" >> $GITHUB_STEP_SUMMARY