Hello

<artifact name="FEATURE-CLI-ENTRYPOINT.md">
# FEATURE: CLI Entry Point

| Field       | Value |
|-------------|-------|
| Version     | 20260812 V1 |
| Description | Provides the executable standard-input and standard-output CommonMark interface. |
| Depends On  | ARCHITECTURE.md |
| Provides    | parser executable |
| Consumes    | parser core, HTML renderer |

## Questions

- None.

## Workflow

The executable reads UTF-8 Markdown from standard input. It parses block structure before inline structure, renders the resulting document as HTML, and writes only rendered HTML to standard output. A successful invocation exits with status `0`.

The executable is named `cmark` and is invokable from the build directory as `./cmark`. It supports the supplied harness's program invocation contract.

## Programmatic Acceptance

Requires: executable=cmark; scope=test

=== AC cli-stdin-stdout ===
Intent: The executable renders Markdown supplied through standard input and exits successfully.

import subprocess

result = subprocess.run(
    ["./cmark"],
    input="# Hello\n\nworld\n",
    capture_output=True,
    text=True,
    encoding="utf-8",
)
print(result.stdout)
print(result.stderr, file=__import__("sys").stderr)
assert result.returncode == 0
assert result.stdout == "<h1>Hello</h1>\n<p>world</p>\n"
=== END AC cli-stdin-stdout ===

=== AC cli-utf8 ===
Intent: The executable accepts UTF-8 Markdown and emits UTF-8 HTML.

import subprocess

result = subprocess.run(
    ["./cmark"],
    input="cafe\n",
    capture_output=True,
    text=True,
    encoding="utf-8",
)
assert result.returncode == 0
assert result.stdout == "<p>cafe</p>\n"
=== END AC cli-utf8 ===

## User Acceptance

- None.

## Guardrails

- Markdown input is read from standard input.
- Rendered HTML is written to standard output.
- The executable does not write diagnostics into standard output during successful parsing.
</artifact>