Rebrand sexp → sx across web platform (173 files)

Rename all sexp directories, files, identifiers, and references to sx.
artdag/ excluded (separate media processing DSL).

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

shared/sx/tests/test_parse_all.py

@@ -0,0 +1,35 @@
+"""Verify every .sx and .sx file in the repo parses without errors."""
+
+import os
+import pytest
+
+from shared.sx.parser import parse_all
+
+
+def _collect_sx_files():
+    """Find all .sx and .sx files under the repo root."""
+    repo = os.path.dirname(os.path.dirname(os.path.dirname(os.path.dirname(
+        os.path.abspath(__file__)
+    ))))
+    files = []
+    for dirpath, _dirs, filenames in os.walk(repo):
+        if "node_modules" in dirpath or ".git" in dirpath or "artdag" in dirpath:
+            continue
+        for fn in filenames:
+            if fn.endswith((".sx", ".sx")):
+                files.append(os.path.join(dirpath, fn))
+    return sorted(files)
+
+
+_SX_FILES = _collect_sx_files()
+
+
+@pytest.mark.parametrize("path", _SX_FILES, ids=[
+    os.path.relpath(p) for p in _SX_FILES
+])
+def test_parse(path):
+    """Each sx file should parse without errors."""
+    with open(path) as f:
+        source = f.read()
+    exprs = parse_all(source)
+    assert len(exprs) > 0, f"{path} produced no expressions"