docs: add CHANGELOG.md from git history in Keep a Changelog format (#8)

Reconstructed from full commit history. Groups changes into 6 releases
(v0.0.1 through v0.4.0) covering the initial lib/ seed, CI/hooks setup,
agent-knowledge submodule, binary resolver, git collector, template fixes,
and the ANALYZER_MIN_VERSION v0.3.0 bump.

Author: avifenesh

CHANGELOG.md

@@ -0,0 +1,64 @@
+# Changelog
+
+All notable changes to agent-core are documented here.
+
+Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
+
+## [Unreleased]
+
+## [0.4.0] - 2026-03-22
+
+### Changed
+
+- Bumped `ANALYZER_MIN_VERSION` to `v0.3.0` in `lib/binary/version.js`. v0.3.0 adds Phase 2-4 of agent-analyzer: AST symbol extraction (6 languages), project metadata, and doc-code cross-references. New query subcommands available: `symbols`, `dependents`, `stale-docs`, `project-info`.
+
+## [0.3.0] - 2026-03-16
+
+### Fixed
+
+- Removed misleading `AUTO-GENERATED - do not edit directly` comment from `templates/CLAUDE.md.tmpl`. Plugin repos are expected to edit the generated file; the comment was incorrect.
+- Removed redundant `Be concise` clause from rule 8 in the template (flagged by agnix as redundant).
+
+## [0.2.0] - 2026-03-15
+
+### Added
+
+- `lib/binary/` - Binary resolver for the `agent-analyzer` Rust binary. Handles lazy download from GitHub releases at runtime (no postinstall hook). Supports 5 platform targets, `tar.gz`/`zip` extraction, version checking, and auto-upgrade. Uses only Node.js built-ins; zero external npm dependencies. Exports `ensureBinary`, `runAnalyzer`, and related utilities.
+- `lib/collectors/git.js` - Git history collector that runs `agent-analyzer repo-intel init` and extracts health metrics: hotspots, contributors, AI ratio, bus factor, conventions, and release info. Registered in the `collect()` dispatch in `lib/collectors/index.js`.
+
+### Changed
+
+- Updated `lib/collectors/git.js` for the `RepoIntelData` schema: added `recentChanges` to hotspot output and `confidence` field to `aiAttribution`.
+
+## [0.1.1] - 2026-03-06
+
+### Added
+
+- Added `agent-knowledge` as a git submodule, centralizing the knowledge base in [agent-sh/agent-knowledge](https://github.com/agent-sh/agent-knowledge) and sharing it across all plugin repos.
+
+## [0.1.0] - 2026-02-22
+
+### Added
+
+- CI workflow calling the reusable workflow from `agent-sh/.github`.
+- Automated Claude Code PR review (restricted to owner/member/collaborator, max 3 runs per PR).
+- Claude Code `@mentions` support in PR comments.
+- Pre-push hook that runs tests before push.
+- agnix validation step in the CI pipeline.
+- CLAUDE.md sync: template (`templates/CLAUDE.md.tmpl`) and generator script (`scripts/generate-claudemd.js`) that produce a consistent `CLAUDE.md` for each consumer plugin repo during the sync workflow.
+- Extended sync matrix to all 12 graduated plugin repos.
+
+## [0.0.1] - 2026-02-21
+
+### Added
+
+- Initial seed: `lib/` directory ported from agentsys, covering platform detection, pattern matching, workflow state, collectors, adapters, and utilities.
+- Sync workflow that triggers `lib/` propagation to consumer repos on push to `main`.
+
+[Unreleased]: https://github.com/agent-sh/agent-core/compare/v0.4.0...HEAD
+[0.4.0]: https://github.com/agent-sh/agent-core/compare/v0.3.0...v0.4.0
+[0.3.0]: https://github.com/agent-sh/agent-core/compare/v0.2.0...v0.3.0
+[0.2.0]: https://github.com/agent-sh/agent-core/compare/v0.1.1...v0.2.0
+[0.1.1]: https://github.com/agent-sh/agent-core/compare/v0.1.0...v0.1.1
+[0.1.0]: https://github.com/agent-sh/agent-core/compare/v0.0.1...v0.1.0
+[0.0.1]: https://github.com/agent-sh/agent-core/releases/tag/v0.0.1