Add canon extension and canon-core preset. (#2022)

* Add canon extension and canon-core preset.

* fix: correct branch and link references for spec-kit-canon catalog entries

- Fix documentation/changelog URLs using `main` → `master` branch in extension and preset catalogs
- Fix preset display link label from `spec-kit-canon-core` → `spec-kit-canon` in README

* chore: refresh community catalog timestamps

* chore: refresh canon extension command count

* chore: point canon catalog entries to repo root instead of subdirectories

---------

Co-authored-by: Manfred Riem <15701806+mnriem@users.noreply.github.com>

README.md

@@ -185,6 +185,7 @@ The following community-contributed extensions are available in [`catalog.commun
 | AI-Driven Engineering (AIDE) | A structured 7-step workflow for building new projects from scratch with AI assistants — from vision through implementation | `process` | Read+Write | [aide](https://github.com/mnriem/spec-kit-extensions/tree/main/aide) |
 | Archive Extension | Archive merged features into main project memory. | `docs` | Read+Write | [spec-kit-archive](https://github.com/stn1slv/spec-kit-archive) |
 | Azure DevOps Integration | Sync user stories and tasks to Azure DevOps work items using OAuth authentication | `integration` | Read+Write | [spec-kit-azure-devops](https://github.com/pragya247/spec-kit-azure-devops) |
+| Canon | Adds canon-driven (baseline-driven) workflows: spec-first, code-first, spec-drift. Requires Canon Core preset installation. | `process` | Read+Write | [spec-kit-canon](https://github.com/maximiliamus/spec-kit-canon/tree/master/extension) |
 | Checkpoint Extension | Commit the changes made during the middle of the implementation, so you don't end up with just one very large commit at the end | `code` | Read+Write | [spec-kit-checkpoint](https://github.com/aaronrsun/spec-kit-checkpoint) |
 | Cleanup Extension | Post-implementation quality gate that reviews changes, fixes small issues (scout rule), creates tasks for medium issues, and generates analysis for large issues | `code` | Read+Write | [spec-kit-cleanup](https://github.com/dsrednicki/spec-kit-cleanup) |
 | Conduct Extension | Orchestrates spec-kit phases via sub-agent delegation to reduce context pollution. | `process` | Read+Write | [spec-kit-conduct-ext](https://github.com/twbrandon7/spec-kit-conduct-ext) |
@@ -241,6 +242,7 @@ The following community-contributed presets customize how Spec Kit behaves — o
 | Preset | Purpose | Provides | Requires | URL |
 |--------|---------|----------|----------|-----|
 | AIDE In-Place Migration | Adapts the AIDE extension workflow for in-place technology migrations (X → Y pattern) — adds migration objectives, verification gates, knowledge documents, and behavioral equivalence criteria | 2 templates, 8 commands | AIDE extension | [spec-kit-presets](https://github.com/mnriem/spec-kit-presets) |
+| Canon Core | Adapts original Spec Kit workflow to work together with Canon extension | 2 templates, 8 commands | — | [spec-kit-canon](https://github.com/maximiliamus/spec-kit-canon) |
 | Pirate Speak (Full) | Transforms all Spec Kit output into pirate speak — specs become "Voyage Manifests", plans become "Battle Plans", tasks become "Crew Assignments" | 6 templates, 9 commands | — | [spec-kit-presets](https://github.com/mnriem/spec-kit-presets) |
 | VS Code Ask Questions | Enhances the clarify command to use `vscode/askQuestions` for batched interactive questioning. | 1 command | — | [spec-kit-presets](https://github.com/fdcastel/spec-kit-presets) |