feat(arch): add arch-metrics command — fan-in/out, instability, god-module detection (closes #61)

[Wolfvin]

Summary

Implements issue #61: architecture metrics command.

Command

codelens arch-metrics [workspace] — computes fan-in, fan-out, instability, and god-module detection from the SQLite graph.

Flags

• --threshold-fanin N (default 10)
• --threshold-fanout N (default 15)
• --sort-by instability|fan-in|fan-out|name

Metrics

• Fan-in: distinct source files with edges pointing TO this module
• Fan-out: distinct target files that edges FROM this module point to
• Instability: fan-out / (fan-in + fan-out) — 0=stable, 1=instable
• God-module: flagged when fan-in > threshold OR fan-out > threshold

Files

• New: scripts/commands/arch_metrics.py
• Synced: command count 65→66 via sync_command_count.py --apply

Verification

• Test suite: 1 pre-existing failure (test_compact_format graph data, unrelated)
• codelens arch-metrics . produces valid JSON output

Closes #61

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud