chore: strip remaining pre-fork version references

Second pass — removes chat-switchboard version numbers from config
field docs, section headers, file headers, and test comments. These
were pre-fork version tags that don't apply to switchboard-core.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/handlers/safe_json.go

@@ -51,7 +51,7 @@ func (s *jsonScanner) Scan(src interface{}) error {
 		// memory on the next rows.Scan() call, corrupting our data after the
 		// fact. This caused intermittent SafeJSON 500s on paginated list
 		// endpoints where row N's Settings pointed to row N+1's overwritten
-		// buffer. Fixed in v0.21.7.
+		// buffer. Fixed.
 		cp := make([]byte, len(v))
 		copy(cp, v)
 		*s.dest = json.RawMessage(cp)