Split raw API command internals

[odyslam]

Supersedes the closed oversized PR #90. This is stack slice 3/8.

Base: codex/pcl-human-output-polish
Head: codex/pcl-api-command-extraction

What changed:

• Extracts raw pcl api command internals by concern.
• Separates manifest/list/inspect/call/coverage handling instead of growing one large command path.
• Preserves the existing raw API debugging surface while making it easier to maintain.

Review focus:

• Mechanical module extraction and unchanged behavior.
• Raw API command parity, especially list/inspect/call/coverage paths.

Validation:

• make ci passed on the stack tip codex/pcl-slim-generated-client.
• Local ./target/debug/pcl api manifest --toon smoke passed.

[odyslam]

Superseded by #98, which now combines the raw API command extraction and workflow output foundation as review step 2/5.