Merge loops/sx-vm-extensions into architecture: serving-mode JIT (opt-in)

Brings the bytecode JIT to the persistent epoch serving mode, gated opt-in via
SX_SERVING_JIT=1 (default OFF → zero change for existing loops). Includes the
correctness fixes that make the JIT match the CEK interpreter, and the
interpret-only exclusions that keep continuation-based guest interpreters safe.

Kernel / shared:
- SX_SERVING_JIT gate in sx_server.ml (loads lib/compiler.sx + register_jit_hook
  only when opted in).
- compiler.sx-as-`compile` correctness: else-symbol in compile-cond/case/guard;
  OP_DIV rational; OP_EQ/_fast_eq rational+ListRef; callable? accepts VmClosure.
- Three composable interpret-only signals in jit_compile_lambda:
  (1) jit-exclude! name / "ns-*" prefix; (2) PUSH_HANDLER recursive bytecode
  scan (guard/handler-bind/Dream catch); (3) jit-exclude-callers-of! +
  code_refs_escaping_caller (call/cc-establishing form callers).

Per-guest interpret-only declarations in each guest runtime: smalltalk (dispatch
core + pharo-test-class), scheme (scheme-*/scm-*), erlang (er-*/erlang-*),
prolog (pl-*), common-lisp (cl-*/clos-* + condition-form callers), js
(js-*/jp-*), haskell (hk-*).

Verified under SX_SERVING_JIT=1 (== CEK, no hang): host 181, smalltalk 847,
scheme/flow 166, erlang 530, prolog 590/mod 390, haskell 285, common-lisp 487,
js 148, apl 152, datalog/forth/ocaml. run_tests --jit 4813/1131 (was 4809/1135,
improved), no-jit 4834/1110 (unchanged). Default-OFF gate => no loop regresses.

plans/jit-bytecode-correctness.md

@@ -203,3 +203,34 @@ general fix is propagate-don't-rerun (run_tests' hook semantics) but that
 surfaces genuine mid-run miscompiles as errors and must land with fixing/
 excluding those — deferred (shared CEK/VM change). The default-OFF gate makes
 all of this opt-in, so nothing regresses by default.
+
+---
+
+## common-lisp residual resolved — call/cc-caller exclusion (2026-06-28)
+
+Investigated the 6 CL opt-in-JIT failures. Findings:
+- **geometry / mop-trace (0/0) are NOT JIT regressions** — they error "Undefined
+  symbol: refl-class-chain-depth-with" on BOTH CEK and JIT (the CLOS suites in
+  conformance.sh don't preload lib/guest/reflective/class-chain.sx). Pre-existing
+  harness gap; not counted in the 6.
+- The **6 real failures** (parse-recover 4, interactive-debugger 2) were all
+  condition-system continuation escape. cl-restart-case/cl-handler-case/
+  cl-handler-bind wrap their body in call/cc. When an SX function driving the
+  condition system (parse-numbers, make-policy-debugger) is JIT-compiled, the
+  call/cc form runs in a NESTED cek-run where invoking the captured continuation
+  runs-to-completion-and-returns instead of escaping → restart fails to abort,
+  body falls through. Seen as accumulation ((1 3 0 3) vs (1 3)) and no-abort
+  (999 sentinel). Also produced a +3 double-execution over-count (490 vs 487).
+
+Fix: a third interpret-only signal beyond name/prefix and PUSH_HANDLER —
+`jit-exclude-callers-of!` registers call/cc-establishing/invoking form names;
+`jit_compile_lambda` skips any function whose constant pool (recursively)
+references one (`code_refs_escaping_caller`). Guarded so it's a no-op for guests
+that don't register. CL registers cl-restart-case/cl-handler-case/cl-handler-bind
+(establish) + cl-invoke-restart/cl-invoke-debugger/cl-signal/cl-error-with-debugger
+(invoke). Result: **CL under SX_SERVING_JIT=1 = 487/0, exactly matching CEK.**
+
+The three interpret-only signals now: (1) name / "ns-*" prefix [jit-exclude!],
+(2) PUSH_HANDLER in bytecode [guard users, structural], (3) references a
+registered escaping form [call/cc-establishing callers]. Together they cover the
+continuation-unsafe surface without a deep VM continuation rewrite.