Bootstrap the standalone changelog package and reusable CLI commands

[coisa]

Summary

Bootstrap a standalone fast-forward/changelog package to own the Fast Forward changelog domain and expose reusable CLI commands for changelog automation.

Problem

Changelog parsing, mutation, rendering, and release-version inference currently live inside fast-forward/dev-tools, while fast-forward/github-actions also needs part of that behavior for workflow automation. Keeping the changelog domain inside dev-tools makes reuse awkward, increases coupling between packages, and blocks the longer-term goal of turning dev-tools into an aggregator of smaller CLI-focused packages.

Goal

Create a standalone fast-forward/changelog package that:

• owns the changelog document model, parser, renderer, and release-oriented domain services;
• provides commands that can run standalone through its own application;
• allows fast-forward/dev-tools and fast-forward/github-actions to register or proxy those commands locally without reimplementing the domain.

Scope

• Create the new fast-forward/changelog package repository and bootstrap it as an installable Composer package.
• Move the generic changelog domain from fast-forward/dev-tools into this package.
• Provide dedicated services for changelog loading, release-note rendering, version inference, promotion, and entry management.
• Provide a standalone Symfony Console application for the package.
• Provide changelog commands that are reusable from other applications.
• Prepare fast-forward/dev-tools and fast-forward/github-actions to depend on this package instead of owning changelog domain logic directly.

Proposed Commands

• changelog:resolve-version
• changelog:render-release-notes
• changelog:entry
• changelog:promote
• changelog:show or an equivalent command name if we consolidate output behavior

Acceptance Criteria

• A new public Composer package named fast-forward/changelog exists under the php-fast-forward organization.
• The package is installable standalone and exposes its own console entrypoint and application class.
• The package does not depend on fast-forward/dev-tools.
• Generic changelog document, parser, renderer, and mutation logic live in the new package.
• The package exposes reusable Symfony Console commands for changelog automation.
• The initial command set covers release-version resolution and release-note rendering at minimum.
• The package structure supports later migration of entry-management and promotion commands without API churn.
• fast-forward/dev-tools can depend on the package and register its commands instead of owning the changelog domain.
• fast-forward/github-actions can depend on the package and inject or proxy the commands it needs.
• README and package metadata describe the standalone CLI use case and the embeddable-command use case.

Non-Goals

• Completing the full migration of every changelog-related command in the same first PR.
• Reworking unrelated GitHub Actions commands or PHP version resolution logic.
• Turning dev-tools into a pure aggregator in this first step beyond the changelog extraction seam.

Notes

• Prefer a package structure that keeps command orchestration thin and pushes changelog behavior into focused services.
• Prefer names and namespaces that make the standalone package readable both when used directly and when embedded into larger console applications.
• Keep output deterministic for workflow and CI usage.