Fix parser escape ordering and prim_get for non-dict objects

Parser: chained .replace() calls processed \n before \\, causing \\n
to become a real newline. Replaced with character-by-character
_unescape_string. Fixes 2 parser spec test failures.

Primitives: prim_get only handled dict and list. Objects with .get()
methods (like PageDef) returned None. Added hasattr fallback.
Fixes 9 defpage spec test failures.

All 259 spec tests now pass (was 244/259).

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

shared/sx/parser.py

@@ -62,6 +62,24 @@ class SxExpr(str):
 # Errors
 # ---------------------------------------------------------------------------
 
+_ESCAPE_MAP = {"n": "\n", "t": "\t", '"': '"', "\\": "\\", "/": "/"}
+
+
+def _unescape_string(s: str) -> str:
+    """Process escape sequences in a parsed string, character by character."""
+    out: list[str] = []
+    i = 0
+    while i < len(s):
+        if s[i] == "\\" and i + 1 < len(s):
+            nxt = s[i + 1]
+            out.append(_ESCAPE_MAP.get(nxt, nxt))
+            i += 2
+        else:
+            out.append(s[i])
+            i += 1
+    return "".join(out)
+
+
 class ParseError(Exception):
     """Error during s-expression parsing."""
 
@@ -141,11 +159,7 @@ class Tokenizer:
                 raise ParseError("Unterminated string", self.pos, self.line, self.col)
             self._advance(m.end() - self.pos)
             content = m.group()[1:-1]
-            content = content.replace("\\n", "\n")
-            content = content.replace("\\t", "\t")
-            content = content.replace('\\"', '"')
-            content = content.replace("\\/", "/")
-            content = content.replace("\\\\", "\\")
+            content = _unescape_string(content)
             return content
 
         # Keyword

shared/sx/primitives.py

@@ -374,6 +374,8 @@ def prim_get(coll: Any, key: Any, default: Any = None) -> Any:
         return default
     if isinstance(coll, list):
         return coll[key] if 0 <= key < len(coll) else default
+    if hasattr(coll, "get"):
+        return coll.get(key, default)
     return default
 
 @register_primitive("len")