docs(readme): convert README.adoc -> Markdown (renders on Glama/profile/community-health) (#27)

README was AsciiDoc → renders as raw markup in Markdown consumers (Glama
MCP directory, GitHub community-health, GitHub profile). pandoc
asciidoc→GFM (badges → clickable), SPDX header kept, duplicate `.adoc`
removed. Part of the estate README-format fix.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: hyperpolymath

README.adoc

@@ -1,61 +1,70 @@
-[![Sponsor](https://img.shields.io/badge/Sponsor-%E2%9D%A4-pink?logo=github)](https://github.com/sponsors/hyperpolymath)
+<!--
+SPDX-License-Identifier: CC-BY-SA-4.0
+SPDX-FileCopyrightText: 2025-2026 Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
+-->
 
-// SPDX-License-Identifier: CC-BY-SA-4.0
-= a2ml-haskell
-Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
-:toc:
-:toc-placement: preamble
+Haskell library for parsing and rendering A2ML (Attested Markup
+Language) — attestation-native markup carrying trust metadata,
+cryptographic attestation fields, and provenance information.
 
-Haskell library for parsing and rendering A2ML (Attested Markup Language)
-— attestation-native markup carrying trust metadata, cryptographic
-attestation fields, and provenance information.
+# Overview
 
-== Overview
+`a2ml-haskell` provides a purely functional parser and renderer over
+`Text`:
 
-`a2ml-haskell` provides a purely functional parser and renderer over `Text`:
+- `Data.A2ML.Parser` — \`parseA2ML  
+  Text → Either ParseError Document\`. Line-oriented, no regex, no
+  mutable state. Recognises headings, multi-line directive blocks
+  (`@name:` `…` `@end`), bullet lists, and inline formatting.
 
-* `Data.A2ML.Parser` — `parseA2ML :: Text -> Either ParseError Document`.
-  Line-oriented, no regex, no mutable state. Recognises headings, multi-line
-  directive blocks (`@name: ... @end`), bullet lists, and inline formatting.
+- `Data.A2ML.Renderer` — serialises a `Document` back to canonical A2ML.
 
-* `Data.A2ML.Renderer` — serialises a `Document` back to canonical A2ML.
+<!-- -->
 
-* `Data.A2ML.Types` — `Document`, `Block`, `Inline`, `DirectiveName`
+- `Data.A2ML.Types` — `Document`, `Block`, `Inline`, `DirectiveName`
   (typed sum: `DirAbstract`, `DirRefs`, `DirAttestation`, `DirMeta`,
-  `DirCustom Text`), `Attestation`, `TrustLevel`, `Manifest`, `Reference`.
+  `DirCustom` `Text`), `Attestation`, `TrustLevel`, `Manifest`,
+  `Reference`.
 
-The Haskell variant uses richer directive syntax than `a2ml-rs`: directives
-are multi-line `@name: ... @end` blocks (not single-line `@name value` pairs).
+The Haskell variant uses richer directive syntax than `a2ml-rs`:
+directives are multi-line `@name:` `…` `@end` blocks (not single-line
+`@name` `value` pairs).
 
-== Attestation Model
+# Attestation Model
 
 The `Attestation` type carries:
 
-* `attestationSigner` — identity of the signing agent or person
-* `attestationAlgorithm` — e.g. `"ed25519"` or `"sha256"`
-* `attestationSignature` — hex or base64 signature (opaque, not verified here)
-* `attestationTimestamp` — optional ISO-8601 timestamp
+- `attestationSigner` — identity of the signing agent or person
+
+- `attestationAlgorithm` — e.g. `"ed25519"` or `"sha256"`
+
+- `attestationSignature` — hex or base64 signature (opaque, not verified
+  here)
+
+- `attestationTimestamp` — optional ISO-8601 timestamp
 
 `TrustLevel` encodes attestor count and independence: `Unsigned` →
 `SelfAttested` → `ThirdPartyAttested` → `MultiAttested`.
 
-`Manifest` aggregates title, author, version, SPDX license, overall trust
-level, and the full attestation list — the entry point for provenance
-inspection.
+`Manifest` aggregates title, author, version, SPDX license, overall
+trust level, and the full attestation list — the entry point for
+provenance inspection.
 
-== Building
+# Building
 
-[source,sh]
-----
+```sh
 cabal build
 cabal test
-----
+```
+
+# Related
 
-== Related
+- [a2ml-rs](https://github.com/hyperpolymath/a2ml-rs) — Rust
+  implementation
 
-* link:https://github.com/hyperpolymath/a2ml-rs[a2ml-rs] — Rust implementation
-* link:https://github.com/hyperpolymath/pandoc-a2ml[pandoc-a2ml] — Pandoc Lua reader/writer
+- [pandoc-a2ml](https://github.com/hyperpolymath/pandoc-a2ml) — Pandoc
+  Lua reader/writer
 
-== License
+# License
 
-MPL-2.0. See link:LICENSE[LICENSE].
+MPL-2.0. See [LICENSE](LICENSE).