Fix Python emitter command arg handling and restore Check Changes compliance

[Copilot]

The failing Check Changes job came from an undocumented change in @typespec/http-client-python. While addressing that, this also fixes the underlying emitter bug where transformed options could be re-added as undefined when command args were assembled.

• Workflow failure

  • Adds the missing Chronus entry for @typespec/http-client-python so pnpm chronus verify --since main recognizes the change.

• Emitter command arg construction

  • Extracts command arg assembly into a dedicated helper in packages/http-client-python/emitter/src/emitter.ts.
  • Treats transformed options (license, packaging-files-config, keep-pyproject-fields) as handled inputs so they are not copied back into the final arg map.
  • Avoids passing undefined values through the generic option copy path.

• Regression coverage

  • Adds a focused emitter test covering the transformed-option path, including keep-pyproject-fields and packaging-files-config.

const commandArgs = buildCommandArgs(
  {
    license: "MIT",
    "package-name": "sample-package",
    "packaging-files-config": {
      README: "README.md",
      LICENSE: "LICENSE.txt",
    },
    "keep-pyproject-fields": {
      authors: true,
      description: true,
    },
  },
  false,
);

// preserved transformed args
commandArgs["packaging-files-config"]; // README:README.md|LICENSE:LICENSE.txt
commandArgs["keep-pyproject-fields"]; // authors,description