docs: Complete Phase 7 - documentation and examples

- Update README with comprehensive API documentation for v0.1.6:
  - Backend availability API (Scalar, SIMD, OpenMP, CUDA)
  - Boundary conditions with all BC types and functions
  - Derived fields and statistics
  - CPU features detection (AVX2, NEON)
  - Error handling with exception classes
  - Migration guide from v0.1.0

- Update MIGRATION_PLAN.md to mark Phase 7 complete

- Add new examples:
  - backend_detection.py - CPU features, solver/BC backend queries
  - boundary_conditions.py - BC types, backends, inlet/outlet
  - channel_flow.py - Parabolic inlet, Poiseuille flow comparison
  - derived_fields.py - Statistics, velocity magnitude, VTK output
  - error_handling.py - Exception classes, raise_for_status
  - lid_driven_cavity_advanced.py - Complete cavity simulation
  - solver_comparison.py - Backend performance benchmarking
  - vtk_output.py - Scalar/vector fields, time series, CSV output

Author: shaia

MIGRATION_PLAN.md

@@ -4,9 +4,9 @@ This document outlines the required changes to update cfd-python bindings to wor
 
 ## Current State
 
-- **cfd-python version:** 0.1.0 (outdated)
+- **cfd-python version:** 0.2.0 (compatible with CFD v0.1.6)
 - **Target CFD library:** v0.1.6
-- **Status:** BROKEN - will not compile against current CFD library
+- **Status:** ✅ COMPLETE - All migration phases finished
 
 ## What's New in v0.1.6
 
@@ -457,37 +457,44 @@ cpu_features_t cfd_get_cpu_features(void);
 
 **Actual effort:** < 0.5 days
 
-### Phase 7: Documentation & Tests (Required)
+### Phase 7: Documentation & Tests (Required) ✅ COMPLETED
 
 **Priority:** P1 - Required for release
 
-**Tasks:**
-
-- [ ] **7.1 Update README**
-  - Installation instructions
-  - API changes documentation
-  - Migration guide for users
-  - Backend availability examples
+**Status:** Completed on 2026-01-03
 
-- [ ] **7.2 Update Python docstrings**
-  - All new functions
-  - BC examples
-  - Error handling examples
-  - Backend detection examples
-
-- [ ] **7.3 Add comprehensive tests**
-  - Test all BC types
-  - Test error handling
-  - Test derived fields
-  - Test with different backends
-  - Test backend availability API
+**Tasks:**
 
-- [ ] **7.4 Update examples**
-  - BC usage examples
-  - Derived fields examples
-  - Backend detection examples
+- [x] **7.1 Update README**
+  - Complete API reference for all v0.1.6 features
+  - Boundary conditions documentation with examples
+  - Backend availability API documentation
+  - Error handling with exception classes
+  - CPU features detection
+  - Migration guide from v0.1.0
+
+- [x] **7.2 Update Python docstrings**
+  - Comprehensive module docstring in `__init__.py`
+  - All BC functions, types, and edges documented
+  - Error handling API documented
+  - Backend availability API documented
+  - CPU features API documented
+
+- [x] **7.3 Add comprehensive tests**
+  - `test_boundary_conditions.py` - All BC types and backends
+  - `test_backend_availability.py` - Backend constants and functions
+  - `test_derived_fields.py` - Statistics and velocity magnitude
+  - `test_errors.py` - Exception classes and raise_for_status
+  - `test_cpu_features.py` - SIMD detection and grid stretching
+  - `test_abi_compatibility.py` - NULL handling and stress tests
+
+- [x] **7.4 Update examples**
+  - `boundary_conditions.py` - BC types, backends, inlet/outlet
+  - `backend_detection.py` - CPU features, solver/BC backends
+  - `derived_fields.py` - Statistics, velocity magnitude, VTK output
+  - `error_handling.py` - Exception classes, raise_for_status
 
-**Estimated effort:** 2 days
+**Actual effort:** < 0.5 days
 
 ---
 
@@ -569,9 +576,9 @@ find_library(CFD_LIBRARY cfd_library)  # Unified library name
 | Phase 4: Error Handling | ~~1 day~~ ✅ < 0.5 days | 4 days |
 | Phase 5: Backend Availability (v0.1.6) | ✅ 0.5 days | 4.5 days |
 | Phase 6: CPU Features | ~~1 day~~ ✅ < 0.5 days | 5 days |
-| Phase 7: Docs & Tests | 2 days | 7 days |
+| Phase 7: Docs & Tests | ~~2 days~~ ✅ < 0.5 days | 5.5 days |
 
-**Total estimated effort:** ~~9-10 days~~ ~7 days (5 days completed)
+**Total estimated effort:** ~~9-10 days~~ ~5.5 days ✅ ALL PHASES COMPLETE
 
 ---
 
@@ -694,3 +701,58 @@ While `_exceptions.py` has type hints, the C extension functions lack type stubs
 2. **Standardize coordinate naming** across grid functions
 3. **Consider IntEnum** for constant groups (SIMD, BC types, backends)
 4. **Optional high-level wrappers** for BC operations (Phase 8 candidate)
+
+---
+
+## Phase 7 (CFD ROADMAP) Status: Python Integration
+
+This section tracks progress on Phase 7 from the main CFD library ROADMAP.md, which covers Python integration.
+
+### 7.1 Python Bindings (P1)
+
+| Task | Status | Notes |
+|------|--------|-------|
+| Complete C extension module | ✅ Done | `cfd_python.c` with Stable ABI (Py_LIMITED_API 3.9+) |
+| NumPy array integration | ⚠️ Partial | Functions accept/return Python lists; NumPy conversion at Python layer |
+| Pythonic API design | ✅ Done | Snake_case naming, native Python types, exception hierarchy |
+| Type hints and stubs | ❌ Pending | Phase 8 in cfd-python ROADMAP - `.pyi` stubs not yet created |
+| Pre-built wheels (manylinux, macOS, Windows) | ✅ Done | CI builds wheels for all platforms; CUDA variant for Linux/Windows |
+
+**C Extension Module Features:**
+- Grid creation (uniform and stretched)
+- Flow field operations
+- Solver registry and creation
+- Simulation API (`run_simulation`, `run_simulation_step`)
+- Boundary conditions (all types: Neumann, Dirichlet, no-slip, inlet, outlet)
+- Derived fields and statistics
+- Error handling with Python exceptions
+- Backend availability API (Scalar, SIMD, OMP, CUDA)
+- CPU features detection (AVX2, NEON)
+
+### 7.2 High-level Python API (P1)
+
+| Task | Status | Notes |
+|------|--------|-------|
+| Problem definition classes | ❌ Pending | Not yet implemented |
+| Mesh generation helpers | ⚠️ Partial | `create_grid`, `create_grid_stretched` available |
+| Post-processing utilities | ⚠️ Partial | `compute_velocity_magnitude`, `compute_flow_statistics` available |
+| Jupyter notebook integration | ❌ Pending | Not yet implemented |
+
+**What's Available:**
+- Low-level C bindings exposed directly to Python
+- Exception hierarchy for error handling (`CFDError` and subclasses)
+- `raise_for_status()` helper for checking C library return codes
+
+**What's Missing:**
+- High-level `Simulation` class for problem setup
+- `BoundaryConditions` builder/context manager pattern
+- Integration with matplotlib/visualization in notebooks
+- Problem templates (lid-driven cavity, channel flow, etc.)
+
+### Summary
+
+Phase 7.1 (Python Bindings) is **largely complete** - the C extension module is functional, builds wheels for all platforms, and provides a working Python API. The main gaps are:
+1. Type stubs for IDE support (Phase 8 in cfd-python)
+2. NumPy direct integration (currently uses list conversion)
+
+Phase 7.2 (High-level Python API) is **not started** - the current API exposes C functions directly without high-level Pythonic wrappers or classes.