Implement pyOCD SWD/JTAG programming support with dynamic target detection

[andrewleech]

Major Features Added

pyOCD Integration

• Add SWD/JTAG programming as alternative to usb bootloader methods
• Optional pyOCD dependency via pyocd extra
• Support for debug probe discovery and management
• Automated target chip selection using dynamic detection

Dynamic Target Detection

• Replace hardcoded target mappings with dynamic API-based detection
• Parse MCU info from sys.implementation._machine strings
• Fuzzy matching algorithm for target selection
• Direct probe-based target detection with fallback to fuzzy matching
• Extensible architecture for future OpenOCD/J-Link support

CLI Integration

• Add --method pyocd option for explicit SWD/JTAG programming
• Add --probe option for specific debug probe selection
• Maintain existing bootloader behavior as default
• Clean integration with existing flash method selection

Architecture Improvements

• Abstract debug probe layer for extensibility
• Target detector abstraction with registry system
• Proper error handling and fallback mechanisms
• Performance optimized with caching and lazy loading

Technical Details

Files Added

• mpflash/flash/debug_probe.py - Debug probe abstraction layer
• mpflash/flash/pyocd_probe.py - pyOCD-specific probe implementation
• mpflash/flash/pyocd_flash.py - pyOCD flash programming interface
• mpflash/flash/pyocd_targets.py - Target detection wrapper functions
• mpflash/flash/dynamic_targets.py - Dynamic target detection engine
• mpflash/cli_pyocd.py - pyOCD-specific CLI commands (future)

Files Modified

• mpflash/common.py - Add FlashMethod enum for different programming methods
• mpflash/flash/__init__.py - Integrate pyOCD into flash method selection
• mpflash/cli_flash.py - Add CLI options for pyOCD method and probe selection
• pyproject.toml - Add optional pyOCD dependency
• mpflash/cli_download.py - Fix unused pytest import

Key Benefits

• No hardware requirements change - existing serial methods remain default
• Automated target selection - no manual target configuration needed
• Extensible design - easy to add OpenOCD, J-Link, etc. in future
• Performance optimized - direct API calls instead of subprocess shells
• Maintainable - eliminates hardcoded target mappings

Usage

# Existing behavior unchanged (serial bootloader methods)
mpflash flash

# Explicit pyOCD SWD/JTAG programming
mpflash flash --method pyocd

# Specific debug probe selection
mpflash flash --method pyocd --probe-id stlink

# Install with pyOCD support
uv sync --extra pyocd

Breaking Changes

None - all existing functionality preserved with same default behavior.

[andrewleech]

Hi @Josverl I'm not sure what your appetite is for large changes or if this a direction you like, but I wanted to use it so claude build it :-)

Also, I haven't code reviewed this at all yet, so feel free to not look at it at all either until I do so and un-draft the PR!

[Josverl]

If you build it, you test it😜

I have found the challenge that in the HIL tests needed. I'm not sure if I have the equipment to test it.

Other than that, if others can benefit from it, I think it is useful