feat: add status subcommand

[montfort]

Summary

• Add devtrail status [path] command that checks installation state, structure completeness, and documentation statistics
• Detects whether DevTrail is installed, verifies expected directories/files, and counts documents by type (ADR, AIDEC, AILOG, ETH, INC, REQ, TDE, TES)
• Graceful handling: non-installed projects get an informative message (not an error), unreadable config/manifest show warnings

Test plan

• test_status_not_installed — empty dir returns exit 0 with "not installed" message
• test_status_with_minimal_install — shows version, language, and correct doc counts
• test_status_incomplete_structure — reports missing directories
• test_status_explicit_path_argument — works with explicit path arg
• cargo clippy — no warnings
• cargo build — compiles cleanly

🤖 Generated with Claude Code

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