feat(cli): Phase 3 PR 2 — devtrail charter audit (3-step orchestration)

[montfort]

Summary

Second of 6 PRs implementing Phase 3 + open frictions. The CLI command that orchestrates the dual-audit + calibrator cycle, using the prompt templates and output schema shipped in PR 1 (#85).

Architecture A1 (orchestration-only) means the CLI does not invoke LLM APIs. The operator pastes resolved prompts into their auditor of choice and saves responses to canonical paths.

Three steps, each invokable independently

$ devtrail charter audit CHARTER-01              # Step 1/3: PREPARE
  → resolves auditor prompts, writes to audit/charters/CHARTER-01/prompts/

$ devtrail charter audit CHARTER-01 --calibrate  # Step 2/3: CALIBRATE
  → validates auditor outputs, resolves calibrator prompt

$ devtrail charter audit CHARTER-01 --finalize   # Step 3/3: FINALIZE
  → validates all 3 outputs, prints external_audit YAML for telemetry

Each step is a filesystem mutation. Files persist between steps — operator can prepare, walk away, come back later, calibrate. Each step prints next-action guidance pointing to exact paths.

Per RFC #82 the resolved prompt is persisted before any external action. The schema's prompt_used field cites which prompt template was used; the calibrator can verify provenance.

Module shape

• src/audit_schema.rs: jsonschema wrapper with oneOf-aware error formatting (mirrors telemetry_schema.rs).
• src/commands/charter/audit.rs: 3-step run dispatch, template resolution, frontmatter parsing, external_audit YAML rendering.

Placeholder set

{{charter_id}}, {{charter_title}}, {{charter_path}}, {{charter_content}}, {{git_range}}, {{git_diff}}, {{ailog_paths}}, {{ailog_contents}}, {{audit_role}}, {{schema_path}}, {{auditor_primary_findings}}, {{auditor_secondary_findings}}. Unknown placeholders are left as literals (no surprise mutations).

Test plan

• 400/400 tests pass (10 new unit + 7 new integration on top of 383 carried forward).
• Schema discriminates auditor vs calibrator outputs via oneOf on audit_role (5 unit tests in audit_schema).
• Template resolution preserves unknown placeholders (literal pass-through).
• Full 3-step cycle test simulates the operator pasting auditor + calibrator responses; finalize prints valid external_audit YAML.
• Calibrate without prior auditor outputs fails with clear <path> not found error.
• Calibrate with malformed auditor output (missing required field) bails with schema validation error.
• Finalize prints both auditor IDs in the rendered YAML for telemetry pasting.
• No version bump — release ships at PR 6.

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