Extract the ClickPipes clap contract and parsing tests

[sdairs]

Parent: #318

Stack position: 5 of 6. This isolates the large ClickPipes clap contract before moving its runtime.

Goal

Move all ClickPipes command-line definitions and parsing coverage into the ClickPipes domain module without changing the user-facing CLI.

Scope

• Move ClickPipeCommands, create/source/schema-discovery/settings sub-enums, argument/field structs, possible-value constants, and parsers.
• Move exhaustive ClickPipes write classification and clap parsing tests with those definitions.
• Preserve the boxed top-level ClickPipes command shape used to control enum size.
• Re-export all existing type names through cloud::cli.
• Leave handlers/builders/client wrappers in place for the following runtime sub-issue.

Acceptance

• Existing crate::cloud::cli::* paths continue to compile through re-exports.
• Every ClickPipes command, flag, default, repeatability rule, and accepted value is unchanged.
• Exhaustive write classification remains compiler-checked without wildcard arms.
• All ClickPipes clap tests pass adjacent to the moved definitions.
• Clippy, rustfmt, and workspace checking pass.

Out of scope

• Moving ClickPipes handlers, builders, output, or CloudClient wrappers.
• Any CLI or API behavior change.