Add cocotb testbench for validating generated bus decoder RTL across APB3, APB4, and AXI4-Lite interfaces (#9)

* Initial plan

* Add cocotb test infrastructure and testbenches for APB3, APB4, and AXI4-Lite

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* Add integration tests, examples, and documentation for cocotb testbenches

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* Address code review feedback: use relative imports and update installation docs

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* Add implementation summary document

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* Merge cocotb dependencies into test group

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

* Add optional cocotb simulation workflow with Icarus Verilog

Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: arnavsacheti <36746504+arnavsacheti@users.noreply.github.com>

.github/workflows/cocotb-sim.yml

@@ -0,0 +1,59 @@
+name: Cocotb Simulation Tests
+
+on:
+  push:
+    branches: [ main ]
+  workflow_dispatch:
+  schedule:
+    # Run weekly on Monday at 00:00 UTC
+    - cron: '0 0 * * 1'
+
+jobs:
+  cocotb-sim:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    strategy:
+      matrix:
+        python-version: ['3.10', '3.12']
+        simulator: ['icarus']
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Set up uv
+        uses: astral-sh/setup-uv@v3
+        with:
+          python-version: ${{ matrix.python-version }}
+      
+      - name: Install HDL Simulator
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y iverilog
+          iverilog -V
+      
+      - name: Install dependencies
+        run: |
+          uv sync --group test
+      
+      - name: Run cocotb integration tests
+        run: |
+          uv run pytest tests/cocotb/testbenches/test_integration.py -v
+      
+      - name: Run cocotb simulation tests (APB4)
+        run: |
+          uv run pytest tests/cocotb/testbenches/test_apb4_runner.py -v -s
+        continue-on-error: true
+        env:
+          SIM: ${{ matrix.simulator }}
+      
+      - name: Upload test logs
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: cocotb-logs-py${{ matrix.python-version }}-${{ matrix.simulator }}
+          path: |
+            **/*.vcd
+            **/sim_build/**/*.log
+          retention-days: 7
+          if-no-files-found: ignore