chore: add CHANGELOG.md and bump version to 2.6.0

- Add comprehensive CHANGELOG.md covering all releases from v1.0.0
- Bump version from 2.5.5 to 2.6.0 (new feature, not patch)

Signed-off-by: Sebastian Mendel <info@sebastianmendel.de>

Author: CybotTM

.claude-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "typo3-docs",
-  "version": "2.5.5",
+  "version": "2.6.0",
   "description": "Create and maintain TYPO3 extension documentation with RST validation",
   "repository": "https://github.com/netresearch/typo3-docs-skill",
   "license": "MIT",

CHANGELOG.md

@@ -0,0 +1,234 @@
+# Changelog
+
+All notable changes to the typo3-docs skill are documented here.
+
+This project follows [Semantic Versioning](https://semver.org/).
+
+## [v2.6.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.6.0) — 2026-02-28
+
+### Added
+
+- **Heading hierarchy validation** — new `validate_headings.py` script checks
+  RST files for TYPO3 heading convention violations:
+  - First section heading not using `=` (h2)
+  - Non-standard underline characters (e.g. `^`)
+  - Skipped heading levels (e.g. h2 directly to h4 without h3)
+
+### Fixed
+
+- **`set -e` crash in `validate_docs.sh`** — `((WARNINGS++))` with `set -e`
+  exits the script when the counter is 0 because bash treats `((0))` as falsy.
+  Replaced all `((VAR++))` with safe `VAR=$((VAR + 1))` arithmetic.
+- **Command injection in heading check** — shell variable was interpolated
+  directly into `python3 -c`; extracted to separate Python script with
+  `sys.argv[1]` for secure filename passing.
+
+## [v2.5.4](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.5.4) — 2026-02-25
+
+### Changed
+
+- Replace generic emails with GitHub references
+- Add skill validation CI job via centralized workflow
+
+## [v2.5.3](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.5.3) — 2026-02-25
+
+### Changed
+
+- Add version validation pre-push hook and `.envrc`
+
+## [v2.5.2](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.5.2) — 2026-02-24
+
+### Fixed
+
+- Align SKILL.md with writing-skills quality standard
+
+### Changed
+
+- Add lint CI (ShellCheck, Markdown, YAML)
+
+## [v2.5.1](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.5.1) — 2026-02-24
+
+### Changed
+
+- Standardize release workflow via centralized CI from skill-repo-skill
+
+## [v2.5.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.5.0) — 2026-02-23
+
+### Changed
+
+- Improve skill based on Claude Code insights analysis
+
+## [v2.4.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.4.0) — 2026-02-22
+
+### Added
+
+- Expand troubleshooting section with common content issues
+
+## [v2.3.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.3.0) — 2026-02-21
+
+### Added
+
+- Image zoom/lightbox support documentation (`:zoom: lightbox`, gallery,
+  inline, lens modes)
+- Enforce screenshot creation in validation
+
+## [v2.2.1](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.2.1) — 2026-02-20
+
+### Fixed
+
+- Update checkpoint patterns for extension assessment
+
+## [v2.2.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.2.0) — 2026-02-19
+
+### Added
+
+- `checkpoints.yaml` for automated extension assessment (TD-01 to TD-22)
+- Mechanical verification of documentation structure
+- LLM-based review for RST quality and completeness
+
+## [v2.1.1](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.1.1) — 2026-02-18
+
+### Fixed
+
+- Remove duplicate hooks declaration (Claude Code auto-loads
+  `hooks/hooks.json`)
+
+## [v2.1.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.1.0) — 2026-02-17
+
+### Added
+
+- **PreToolUse hook** — validates RST syntax before writing to
+  `Documentation/*.rst` files
+- Detects common Markdown-to-RST conversion issues
+- Quick reference for TYPO3 RST syntax in warnings
+
+## [v2.0.2](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.0.2) — 2026-02-16
+
+### Fixed
+
+- Correct `plugin.json` version to match tag
+
+## [v2.0.1](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.0.1) — 2026-02-16
+
+### Fixed
+
+- Update `plugin.json` version to match v2.0.0 release
+
+## [v2.0.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v2.0.0) — 2026-02-15
+
+### Breaking
+
+- **Renamed `templates/` to `assets/`** — update any references from
+  `templates/AGENTS.md` to `assets/AGENTS.md`
+
+### Changed
+
+- Rewritten SKILL.md with imperative/trigger-based writing style
+- Complete documentation of all 15 references, 11 scripts, and 1 asset template
+- Fixed non-existent `watch_docs.sh` script reference
+- Updated internal path references in `add-agents-md.sh` and `README.md`
+
+## [v1.9.3](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.9.3) — 2026-02-14
+
+### Changed
+
+- Reduced SKILL.md size from 12,990 to 3,505 bytes (73% reduction)
+
+## [v1.9.2](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.9.2) — 2026-02-13
+
+### Fixed
+
+- Fix skills path format for Claude Code compatibility
+
+## [v1.9.1](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.9.1) — 2026-02-12
+
+### Changed
+
+- Restructured skill for Claude Code compatibility (`skills/typo3-docs/`
+  subdirectory)
+
+## [v1.9.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.9.0) — 2026-02-11
+
+### Added
+
+- Claude Code plugin structure (`plugin.json`, `.claude-plugin/`)
+
+## [v1.8.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.8.0) — 2026-02-10
+
+### Changed
+
+- Prefer `literalinclude` for complete code examples (5+ lines)
+- File naming convention with underscore prefix for code snippet files
+- Text markers (`:start-after:`, `:end-before:`) documentation
+- Updated decision guide and pre-commit checklist
+
+## [v1.7.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.7.0) — 2026-02-09
+
+### Added
+
+- Content directives guide (accordion, admonitions, cards, tabs, tables)
+- Code structure elements guide (code-block, literalinclude, confval, PHP
+  domain)
+- Coding guidelines (.editorconfig, formatting, heading hierarchy)
+- Init command workflow, live-view watch mode, screenshot guide
+- Architecture Decision Records (ADR) documentation
+
+## [v1.6.1](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.6.1) — 2026-02-08
+
+### Fixed
+
+- Concise `composer.json` description, update email to `info@netresearch.de`
+
+## [v1.6.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.6.0) — 2026-02-07
+
+### Added
+
+- Warning about committing `Documentation-GENERATED-temp`
+- Standardized installation, `composer.json`, release workflow
+
+## [v1.5.3](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.5.3) — 2026-02-06
+
+### Changed
+
+- Prefer `guides.xml` (modern PHP-based rendering) over `Settings.cfg`
+- Add webhook status codes to intercept-deployment reference
+- GitHub CLI automation examples for webhook setup
+- Fix `validate_docs.sh` to accept either `guides.xml` or `Settings.cfg`
+
+## [v1.5.2](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.5.2) — 2026-02-05
+
+### Fixed
+
+- `schemaLocation` path — use `../vendor/` (relative from `Documentation/`)
+- Clarified format as `namespace-URI schema-path` pair
+
+## [v1.5.1](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.5.1) — 2026-02-04
+
+### Fixed
+
+- `guides.xml` theme syntax — `theme` must be attribute on `<guides>`, not a
+  child element
+- `schemaLocation` URL — docs.typo3.org schema URL returns 404, use vendor
+  path instead
+
+## [v1.5.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.5.0) — 2026-02-03
+
+### Added
+
+- `guides.xml` configuration reference with full template
+- Extension attributes reference, common inventory URLs
+- Warning about deprecated `<theme>` element
+
+## [v1.4.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.4.0)
+
+### Changed
+
+- TYPO3 extension documentation skill for Claude Code
+
+## [v1.2.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.2.0)
+
+- Release v1.2.0
+
+## [v1.0.0](https://github.com/netresearch/typo3-docs-skill/releases/tag/v1.0.0)
+
+- Initial release