feat(validator): recognise s-expression identity/version fields (#26)

## Summary

Extend the identity-field and version-field regexes so they recognise
s-expression form (\`(name \"...\")\`) alongside the existing TOML form
(\`name = \"...\"\`). Same semantics, only syntax differs.

## Why

The current regex only matches TOML kv pairs:

\`\`\`bash
[[ \"\$line\" =~ ^[[:space:]]*(agent[-_]id|name|project)[[:space:]]*= ]]
\`\`\`

Some valid A2ML dialects in the hyperpolymath estate use Lisp-style
s-expressions for the metadata block — e.g. classification registries:

\`\`\`a2ml
(assail-classifications
  (metadata
    (version \"1.1.0\")
    (project \"boj-server\")))
\`\`\`

These flag as \"Missing required identity field\" today even though
\`project\` is structurally present. \`boj-server\`'s
\`audits/assail-classifications.a2ml\` is the case that surfaced this —
its Dogfood Gate has been red on main for 5+ consecutive runs purely on
this false-positive.

## Patch

Adds two parallel s-expression branches with explanatory comments. Match
\`(field \"...\"\` at any indent so the metadata-block-nested form is
recognised.

## Test plan

- [x] \`bash -n validate-a2ml.sh\` — syntax check passes
- [x] Synthetic fixture with \`(metadata (project \"boj-server\"))\` → 0
errors
- [x] Actual boj-server \`audits/assail-classifications.a2ml\` → 0
errors (was 1)
- [x] Negative control with neither kv nor s-expression identity → still
errors as expected
- [ ] CI on this PR (action self-test, if present)

## Downstream

Once this lands and gets tagged, repos that pin a SHA can bump:

- \`hyperpolymath/boj-server/.github/workflows/dogfood-gate.yml\` —
pinned to \`59145c7d1039fa3059b3ecacdb50ee23d7505898\`. After this
merges, bump to the new SHA to clear the recurring Dogfood Gate failure
on main.

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

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

validate-a2ml.sh

@@ -129,13 +129,27 @@ validate_a2ml() {
         line_num=$((line_num + 1))
 
         # Check for identity fields (various A2ML patterns)
+        # TOML/kv form: `name = "..."`, `project = "..."`, `agent-id = "..."`
         if [[ "$line" =~ ^[[:space:]]*(agent[-_]id|name|project)[[:space:]]*= ]]; then
             has_identity=true
         fi
-        # Check for version field
+        # S-expression form: `(name "...")`, `(project "...")`,
+        # `(agent-id "...")`. Some A2ML dialects (audit registries,
+        # classification stores) use Lisp-style s-expressions for the
+        # metadata block instead of TOML. Identity carries the same
+        # semantics; only the syntax differs. Match at any indent so it
+        # also picks up entries nested under `(metadata ...)`.
+        if [[ "$line" =~ ^[[:space:]]*\([[:space:]]*(agent[-_]id|name|project)[[:space:]]+\" ]]; then
+            has_identity=true
+        fi
+        # Check for version field — TOML form
         if [[ "$line" =~ ^[[:space:]]*(version|schema_version)[[:space:]]*= ]]; then
             has_version=true
         fi
+        # Version field — s-expression form
+        if [[ "$line" =~ ^[[:space:]]*\([[:space:]]*(version|schema_version)[[:space:]]+\" ]]; then
+            has_version=true
+        fi
     done < "$file"
 
     # AI manifest files (0-AI-MANIFEST.a2ml, 0.1-AI-MANIFEST.a2ml, etc.)