Merge eval.sx + frames.sx + cek.sx into single evaluator.sx

The core spec is now one file: spec/evaluator.sx (2275 lines).
Three parts:
  Part 1: CEK frames — state and continuation frame constructors
  Part 2: Evaluation utilities — call, parse, define, macro, strict
  Part 3: CEK machine — the sole evaluator

Deleted:
- spec/eval.sx (merged into evaluator.sx)
- spec/frames.sx (merged into evaluator.sx)
- spec/cek.sx (merged into evaluator.sx)
- spec/continuations.sx (dead — CEK handles shift/reset natively)

Updated bootstrappers (JS + Python) to load evaluator.sx as core.
Removed frames/cek from SPEC_MODULES (now part of core).

Bundle size: 392KB → 377KB standard, 418KB → 403KB full.
All tests unchanged: JS 747/747, Full 864/870, Python 679/679.

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

hosts/python/bootstrap.py

@@ -1484,15 +1484,14 @@ def compile_ref_to_py(
             spec_mod_set.add("page-helpers")
         if "router" in SPEC_MODULES:
             spec_mod_set.add("router")
-    # CEK is the canonical evaluator — always include
-    spec_mod_set.add("cek")
-    spec_mod_set.add("frames")
+    # CEK is always included (part of evaluator.sx core file)
+    has_cek = True
     has_deps = "deps" in spec_mod_set
-    has_cek = "cek" in spec_mod_set
 
     # Core files always included, then selected adapters, then spec modules
+    # evaluator.sx = merged frames + eval utilities + CEK machine
     sx_files = [
-        ("eval.sx", "eval"),
+        ("evaluator.sx", "evaluator (frames + eval + CEK)"),
         ("forms.sx", "forms (server definition forms)"),
         ("render.sx", "render (core)"),
     ]