Architecture Issue 3: Add procedure complexity metrics

[harumiWeb]

Summary

Calculate maintainability metrics for VBA procedures and optionally report configurable thresholds.

Initial metrics

• cyclomatic complexity
• maximum nesting depth
• statement count
• source line count
• branch count
• loop count
• GoTo count
• number of exit points
• parameter count
• ByRef parameter count
• local variable count
• call fan-out

Requirements

• Produce metrics independently from diagnostics.
• Expose metrics through JSON.
• Allow thresholds to be configured separately.
• Keep subjective threshold diagnostics opt-in initially.
• Exclude generated or configured paths where appropriate.
• Ensure single-line and multiline syntax are counted consistently.

Acceptance criteria

• Metrics are deterministic.
• JSON output has a versioned schema.
• Thresholds can be configured or disabled.
• Tests cover nested branches, loops, labels, and properties.
• Metrics can be consumed by future reporting features.