Add subcommand to output parsed commit message as structured data

[vabatta]

Problem

When consuming cz in CI pipelines, it's common to need the parsed scope from a commit message for secondary processing — for example, counting how many service scopes a PR title declares, or routing logic based on type/scope.

Currently the only way to extract these fields is to replicate cz's internal regex (^([a-z]+)(\(([a-zA-Z0-9_@/,*-]+)\))?(!)?: (.+)$) with a grep in the calling script. This is fragile: if the regex in cz ever changes, consumers silently diverge.

Proposed solution

Add a subcommand (e.g. cz extract or extend cz lint) that reads a commit message from stdin and outputs the parsed fields in a machine-readable format (e.g. newline-separated key=value or JSON):

type=feat
scope=teams-mcp,mcp-server-module
breaking=false
description=add cross-service feature

Or as a flag on cz lint:

echo "feat(teams-mcp): add feature" | cz lint --output fields

Use case example

In our gatekeeper CI we need to count how many service scopes a PR title declares and emit a warning when more than one is present:

SCOPE=$(printenv PR_TITLE | grep -oP '^[a-z]+\(\K[^)]+' || true)

This works today but duplicates internal parsing logic. A first-class extraction command would make this more robust and keep consumers in sync with cz's own parser.