Implements and modifies Symfony Profiler Data Collectors with toolbar panels, Twig templates, and service registration. Use when creating, editing, or debugging data collectors for profiling, performance monitoring, or custom metrics visualization in the Web Debug Toolbar. Also use this skill when working with DataCollectorInterface, LateDataCollectorInterface, AbstractDataCollector, cloneVar(), profiler_dump(), or the data_collector service tag — even if the user doesn't explicitly mention "data collector".
Creates and maintains CHANGELOG.md files following the Keep a Changelog 1.1.0 specification. Use when creating a new changelog, adding entries for new releases, documenting changes in Unreleased section, tagging versions, writing release notes, or reviewing existing changelogs for compliance. Also use when working with SemVer version bumps, yanked releases, or comparison links between versions.
Generate structured documentation for Symfony bundles in Markdown with Mermaid diagrams. Use when creating bundle READMEs, documenting architecture, component catalogs, configuration references, integration guides, or ADRs. Also use when the project is a reusable Composer package rather than a full application -- even if the user just says 'write docs' or 'document the architecture'.