cl: Phase 4 CLOS complete — generic functions, multi-dispatch, method qualifiers, 437/437 tests

- lib/common-lisp/clos.sx (27 forms): class registry (8 built-in classes),
  defclass/make-instance/slot-value/slot-boundp/change-class, defgeneric/defmethod
  with :before/:after/:around, clos-call-generic (standard combination: sort by
  specificity, fire befores, call primary chain, fire afters reversed),
  call-next-method/next-method-p, with-slots, deferred accessor installation
- lib/common-lisp/tests/clos.sx: 41 tests (class-of, subclass-of?, defclass,
  make-instance, slot ops, inheritance, method specificity, qualifiers, accessors,
  with-slots, change-class)
- lib/common-lisp/tests/programs/geometry.sx: 12 tests — intersect generic
  dispatching on geo-point×geo-point, geo-point×geo-line, geo-line×geo-line,
  geo-line×geo-plane (multi-dispatch by class precedence)
- lib/common-lisp/tests/programs/mop-trace.sx: 13 tests — :before/:after
  tracing on area and describe-shape generics, call-next-method in circle/rect
- eval.sx: dynamic variables — cl-apply-dyn saves/restores global slot for
  specials; cl-mark-special!/cl-special?/cl-dyn-unbound; defvar now marks
  specials; let/let* rebind via cl-apply-dyn; 8 new tests (182 eval total)
- conformance.sh + test.sh: Phase 4 suites wired in
- plans/common-lisp-on-sx.md: Phase 4 + dynamic variable boxes ticked

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/common-lisp/scoreboard.json

@@ -1,14 +1,17 @@
 {
-  "generated": "2026-05-05T11:24:34Z",
-  "total_pass": 363,
+  "generated": "2026-05-05T11:37:47Z",
+  "total_pass": 437,
   "total_fail": 0,
   "suites": [
     {"name": "Phase 1: tokenizer/reader", "pass": 79, "fail": 0},
     {"name": "Phase 1: parser/lambda-lists", "pass": 31, "fail": 0},
-    {"name": "Phase 2: evaluator", "pass": 174, "fail": 0},
+    {"name": "Phase 2: evaluator", "pass": 182, "fail": 0},
     {"name": "Phase 3: condition system", "pass": 59, "fail": 0},
     {"name": "Phase 3: restart-demo", "pass": 7, "fail": 0},
     {"name": "Phase 3: parse-recover", "pass": 6, "fail": 0},
-    {"name": "Phase 3: interactive-debugger", "pass": 7, "fail": 0}
+    {"name": "Phase 3: interactive-debugger", "pass": 7, "fail": 0},
+    {"name": "Phase 4: CLOS", "pass": 41, "fail": 0},
+    {"name": "Phase 4: geometry", "pass": 12, "fail": 0},
+    {"name": "Phase 4: mop-trace", "pass": 13, "fail": 0}
   ]
 }