Fix markdown metadata propagation, silent pin drops, and mermaid keyword gaps

[Copilot]

Deep analysis of emitter pipeline revealed three bugs and one missing CLI feature.

Bug fixes

• emit_markdown.py: canonical_dict not passed to _get_special_function() in the special pins section and single-ended table — TOML-only profiles (nRF52840, ATmega328P, etc.) always showed "General Purpose I/O" instead of actual special function descriptions
• emit_markdown.py / emit_mermaid.py: Pins with no numeric characters in their name silently dropped from output (guarded by if num_match: with no else branch). Uses float("inf") as fallback sort key so they sort last instead of vanishing
• emit_mermaid.py: _group_pins_by_function() and _get_node_style() missing SCK, TX, RX, CS, SS keywords — standalone nets like SCK miscategorized as "Digital I/O" instead of "Communication"

Enhancement

• cli.py: Added --version flag

Before/after (markdown special functions)

# Before: TOML profile metadata ignored, falls back to hardcoded table
_get_special_function(pin, mcu_lower)  # → "General Purpose I/O" for custom MCUs

# After: canonical_dict propagated, profile metadata used
_get_special_function(pin, mcu_lower, canonical_dict)  # → "NFC Antenna Pin" etc.

12 regression tests added in test_fixes_61_64.py.

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[Copilot]

Pull request overview

This PR fixes three bugs in the emitter pipeline and adds a --version flag to the CLI. The bugs were causing incorrect output for TOML-defined MCU profiles and silently dropping pins with non-numeric names.

Changes:

• Fixed emit_markdown.py to pass canonical_dict to _get_special_function() so TOML profiles display correct special function metadata instead of "General Purpose I/O"
• Fixed silent pin drops in both emit_markdown.py and emit_mermaid.py by using float("inf") as fallback sort key for pins without numeric characters
• Added missing communication protocol keywords (SCK, TX, RX, CS, SS) to Mermaid grouping and styling functions
• Added --version flag to CLI displaying "0.1.0" from pyproject.toml

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tools/pinmapgen/emit_markdown.py	Fixed metadata propagation to _get_special_function() calls (line 85, 219) and added fallback sort key for non-numeric pins (line 218)
tools/pinmapgen/emit_mermaid.py	Added fallback sort key for non-numeric pins (line 108) and expanded communication keyword lists in two functions (lines 266-269, 329-332)
tools/pinmapgen/cli.py	Added --version argument displaying version "0.1.0" (lines 102-104)
tests/test_fixes_61_64.py	Added 12 regression tests covering all four issues (#61-#64) with proper test structure following codebase conventions