Make int32 config parsing strict and loud (#266)

Previously `_extract_value_int32` silently returned the field default when a
config value was present but not an `int32_value` (e.g. a bare `2` instead of
`2i32`). That silent fallback masked malformed input.

Now the helper errors loudly (`ParseError`) when a config value is present with
the wrong type, while still keeping the `i32` suffix requirement and returning
the default only when the field is genuinely absent.

Edited `meta/src/meta/grammar.y` and regenerated the Python, Julia, and Go
parsers. Added regression tests in the Julia and Python SDKs covering: a
properly-typed `2i32` parses, a bare `2` raises `ParseError`, and omitting the
field yields the default (1).

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: hbarthels

meta/src/meta/grammar.y

@@ -1456,9 +1456,11 @@ export_iceberg_config
 
 
 def _extract_value_int32(value: Optional[logic.Value], default: int) -> Int32:
-    if value is not None and builtin.has_proto_field(builtin.unwrap_option(value), 'int32_value'):
+    if value is None:
+        return builtin.int64_to_int32(default)
+    if builtin.has_proto_field(builtin.unwrap_option(value), 'int32_value'):
         return builtin.unwrap_option(value).int32_value
-    return builtin.int64_to_int32(default)
+    builtin.error("expected an int32 value (e.g. `1i32`) for this config field")
 
 
 def _extract_value_int64(value: Optional[logic.Value], default: int) -> int: