Add 68 new tests: continuations-advanced + render-advanced (938/938)

test-continuations-advanced.sx (41 tests):
  multi-shot continuations, composition, provide/context basics,
  provide across shift, scope/emit basics, scope across shift

test-render-advanced.sx (27 tests):
  nested components, dynamic content, list patterns,
  component patterns, special elements

Bugs found and documented:
- case in render context returns DOM object (CEK dispatches case
  before HTML adapter sees it — use cond instead for render)
- context not visible in shift body (correct: shift body runs
  outside the reset/provide boundary)
- Multiple shifts consume reset (correct: each shift needs its own
  reset)

Python runner: skip test-continuations-advanced.sx without --full.

JS 815/815 standard, 938/938 full, Python 706/706.

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

hosts/python/tests/run_tests.py

@@ -273,7 +273,7 @@ for expr in parse_all(framework_src):
 args = [a for a in sys.argv[1:] if not a.startswith("--")]
 
 # Tests requiring optional modules (only with --full)
-REQUIRES_FULL = {"test-continuations.sx", "test-types.sx", "test-freeze.sx", "test-strict.sx", "test-cek.sx"}
+REQUIRES_FULL = {"test-continuations.sx", "test-continuations-advanced.sx", "test-types.sx", "test-freeze.sx", "test-strict.sx", "test-cek.sx"}
 
 test_files = []
 if args: