chore(a2ml): remove 8 deprecated legacy-Scheme example dups (Item 10) (#78)

## What
Orthogonal cleanup slice of **Item 10** — *not* the STATE v2 conversion
workstream (#77, modshells#43).

Deletes the 8 deprecated `*-a2ml/examples/{minimal,comprehensive}.scm`
files in `agentic-a2ml`, `meta-a2ml`, `neurosym-a2ml`, `playbook-a2ml`.
Each:
- self-declares `DEPRECATED … legacy Guile Scheme (.scm) format`
- has a verified, non-trivial `.a2ml` sibling already present

Also repoints the only in-repo references — the `meta-a2ml` and
`playbook-a2ml` `README.adoc` example link lists — from `examples/*.scm`
→ `examples/*.a2ml`, so no doc links break.

## Scope
PRESERVE policy unchanged: `guix.scm`/`channels`/`manifest`, tree-sitter
queries, executable `(define-module)` Guile, and `.scm`-suffixed
satellite/repo path names are untouched. No overlap with the
STATE.scm→v2 converter work.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: hyperpolymath

meta-a2ml/README.adoc

@@ -213,8 +213,8 @@ The formal specification is in the `spec/` directory:
 
 See the link:examples/[examples/] directory:
 
-* link:examples/minimal.scm[minimal.scm] - Minimal valid META file
-* link:examples/comprehensive.scm[comprehensive.scm] - Full-featured example
+* link:examples/minimal.a2ml[minimal.a2ml] - Minimal valid META file
+* link:examples/comprehensive.a2ml[comprehensive.a2ml] - Full-featured example
 
 == Integration with STATE.a2ml
 

playbook-a2ml/README.adoc

@@ -216,8 +216,8 @@ The formal specification is in the `spec/` directory:
 
 See the link:examples/[examples/] directory:
 
-* link:examples/minimal.scm[minimal.scm] - Minimal valid PLAYBOOK
-* link:examples/comprehensive.scm[comprehensive.scm] - Full-featured example
+* link:examples/minimal.a2ml[minimal.a2ml] - Minimal valid PLAYBOOK
+* link:examples/comprehensive.a2ml[comprehensive.a2ml] - Full-featured example
 
 == Conformance Requirements