[2/5] API command and workflow output foundation

[odyslam]

Supersedes the closed oversized PR #90 and consolidates the previous raw-API extraction / output-contract slices (#97 + #98).

Review order

1. [1/5] Human CLI output and agent contract guards #96: Human CLI output and agent contract guards
2. [2/5] API command and workflow output foundation #98: API command and workflow output foundation ← this PR
3. [3/5] Workflow contract and module architecture #100: Workflow contract and module architecture
4. [4/5] OpenAPI operation routing for workflows #101: OpenAPI operation routing for workflows
5. [5/5] Generated-client pruning and stale API cleanup #102: Generated-client pruning and stale API surface cleanup

Base / head

Base: codex/pcl-human-output-polish
Head: codex/pcl-output-contract-workflows

What changed

• Splits raw pcl api internals by concern instead of keeping one growing command path.
• Refactors CLI output contracts and workflow subcommands on top of the human-output work.
• Preserves completion behavior, clap-native root help, auth recovery guidance, and dry-run guidance.

Review focus

• Raw API command parity for list, inspect, call, coverage, and manifest paths.
• Output contract compatibility for human, TOON, JSON, and JSONL login behavior.
• Whether the API/output foundation gives later workflow PRs an obvious place to plug in.

Validation

Validated on the final stack tip codex/pcl-slim-generated-client:

• make ci
• Local ./target/debug/pcl discovery smoke for LLM guide, doctor, auth ensure, whoami, workflows, schema list, and API manifest.