[1/5] Human CLI output and agent contract guards

[odyslam]

Supersedes the closed oversized PR #90 and consolidates the first two split PRs (#95 + #96).

Review order

1. [1/5] Human CLI output and agent contract guards #96: Human CLI output and agent contract guards ← this PR
2. [2/5] API command and workflow output foundation #98: API command and workflow output foundation
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: main
Head: codex/pcl-human-output-polish

What changed

• Establishes the human-mode CLI output improvements as one coherent review slice.
• Keeps TOON/JSON envelopes as the machine contract while making default output more useful for people.
• Preserves agent-facing behavior and adds/updates coverage around output modes.
• Consolidates output/table rendering helpers so follow-up command work has fewer paths to update.

Review focus

• Human output should improve without changing --toon / --json contracts.
• Help, parse, auth, workflow, and destructive-command output should remain mode-aware.
• Renderer consolidation should make future command additions simpler.

Validation

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

• make ci
• ./target/debug/pcl --toon --llms
• ./target/debug/pcl doctor --toon
• PCL_AUTH_NO_BROWSER=1 ./target/debug/pcl auth ensure --toon
• ./target/debug/pcl whoami --toon
• ./target/debug/pcl workflows --toon
• ./target/debug/pcl schema list --toon
• ./target/debug/pcl api manifest --toon