test(parse): add clap micro-conformance

[jdx]

Summary

• add a paired clap/usage typed-CLI harness that compares accepted argv, terminal status/stream, diagnostics, help semantics, and version output
• add the first setting-specific row for require_equals
• match clap's equals-specific diagnostic and render = in typed help placeholders

This establishes the executable harness for the larger generated micro-conformance PLAN item; later stack PRs can add matrix rows without mixing harness design into every feature test.

Validation

• cargo test -p usage-conformance --test clap_micro --all-features
• cargo test -p usage-argv --all-features
• cargo clippy --workspace --all-features --all-targets -- -D warnings

This PR was generated by Codex.

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Note

Medium Risk
Changes the public parse-error enum and help/spec usage rendering, which can break embedders that treated empty-argv help as Error::Help. Behavior is test-covered but is a user-visible CLI contract change.

Overview
Adds a paired clap/usage typed-CLI harness (clap_micro) that compares accepted argv, typed values, error kinds, exit status/stream, help, and version for the first matrix rows (require_equals, defaults, delimiters, hyphen/negative values, enums, arity, globals, groups, external subcommands, and command policies).

Splits arg_required_else_help into Error::MissingArgsHelp so generated parse() prints short help to stderr and exits 2, matching clap, instead of treating it as an explicit help request.

Aligns require_equals presentation: missing-value diagnostics now say an equals is required, and help/spec usage render --flag=<VAL> / --flag[=VAL], including round-trip parsing of those forms.

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[jdx]

Addressed in the owning PR: missing-argument help now selects ANSI color from stderr, while ordinary help continues to inspect stdout. I also fixed the fleet failure this conformance work exposed by rendering require_equals as --flag=<VALUE> in usage-lib, matching usage-argv.

This comment was generated by Codex.

[jdx]

Addressed in #1133: reference documentation now uses = for require_equals, and the regression covers both interactive and reference usage strings.

This comment was generated by Codex.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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