docs(readme): convert README.adoc -> Markdown README.md

README must be real Markdown to render in GitHub community-health, the GitHub
profile, and external MCP directories (Glama) — AsciiDoc shows as raw markup
there. pandoc asciidoc->GFM, badges fixed to clickable, SPDX header kept as an
HTML comment, duplicate README.adoc removed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: hyperpolymath

README.adoc

@@ -1,59 +1,61 @@
-[![Sponsor](https://img.shields.io/badge/Sponsor-%E2%9D%A4-pink?logo=github)](https://github.com/sponsors/hyperpolymath)
-
-= a2ml-pre-commit
-:toc: preamble
-:icons: font
+<!--
+SPDX-License-Identifier: CC-BY-SA-4.0
+SPDX-FileCopyrightText: 2025-2026 Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
+-->
 
-== Overview
+# Overview
 
 **Pre-commit hook for validating A2ML manifest files.**
 
-A2ML (Agnostic Agent Markup Language) is a manifest format for machine-readable
-metadata, AI agent instructions, and project state. This hook validates `.a2ml`
-files on commit for structural correctness and required fields.
+A2ML (Agnostic Agent Markup Language) is a manifest format for
+machine-readable metadata, AI agent instructions, and project state.
+This hook validates `.a2ml` files on commit for structural correctness
+and required fields.
+
+# Checks Performed
+
+1.  **SPDX header** — `SPDX-License-Identifier` in the first 10 lines
+
+2.  **Identity fields** — Requires `agent-id`, `name`, or `project`
+    (relaxed for AI-MANIFEST files)
 
-== Checks Performed
+3.  **Version field** — `version` or `schema_version` presence
 
-1. **SPDX header** — `SPDX-License-Identifier` in the first 10 lines
-2. **Identity fields** — Requires `agent-id`, `name`, or `project` (relaxed for AI-MANIFEST files)
-3. **Version field** — `version` or `schema_version` presence
-4. **Attestation blocks** — Validates `proof`/`signature`/`hash` fields if `[attestation]` section exists
+4.  **Attestation blocks** — Validates `proof`/`signature`/`hash` fields
+    if `[attestation]` section exists
 
-== Installation
+# Installation
 
 Add to your `.pre-commit-config.yaml`:
 
-[source,yaml]
-----
+```yaml
 repos:
   - repo: https://github.com/hyperpolymath/a2ml-pre-commit
     rev: v1.0.0
     hooks:
       - id: validate-a2ml
-----
+```
 
 Then install:
 
-[source,bash]
-----
+```bash
 pre-commit install
-----
+```
 
-== Manual Usage
+# Manual Usage
 
 You can also run the hook script directly:
 
-[source,bash]
-----
+```bash
 ./hooks/validate-a2ml.sh path/to/file.a2ml [more-files.a2ml ...]
-----
+```
 
-== Author
+# Author
 
-Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
+Jonathan D.A. Jewell \<[j.d.a.jewell@open.ac](j.d.a.jewell@open.ac).uk\>
 
-== License
+# License
 
 SPDX-License-Identifier: CC-BY-SA-4.0
 
-See link:LICENSE[LICENSE] for details.
+See [LICENSE](LICENSE) for details.