refactor: companion FrameServer and related (substantive only, no Black)

Reapply refactor from ce8381a (replace monolithic FrameServer with thin
pymc_core subclass, re-export constants, SQLite persistence hooks) while
preserving pre-refactor whitespace where patch applied cleanly. Remaining
files match refactor commit exactly. Diff vs ce8381a is whitespace-only.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/setup-build-env.sh

@@ -23,7 +23,7 @@ log_error() {
 }
 
 # Check if running as root or with sudo
-if [ "$EUID" -ne 0 ]; then 
+if [ "$EUID" -ne 0 ]; then
     log_error "This script must be run with sudo or as root"
     exit 1
 fi