fix(typing): re-export OutputCollector from the function modules

The documented examples import OutputCollector from the function-base
modules (e.g. `from vgi.table_in_out_function import OutputCollector`,
`from vgi.table_buffering_function import OutputCollector`). That works at
runtime, but downstream projects type-checking with `mypy --strict` got:

  Module "vgi.table_in_out_function" does not explicitly export attribute
  "OutputCollector"  [attr-defined]

because the name was only imported from vgi_rpc.rpc, not listed in
__all__. Add OutputCollector to __all__ in table_in_out_function and
table_buffering_function (vgi.table_function already exported it), and in
copy_from_function, whose abstract read() hook also receives an
OutputCollector (moving its import out of the TYPE_CHECKING block so the
re-export exists at runtime).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: rustyconover

vgi/copy_from_function.py

@@ -33,10 +33,11 @@
 
 from abc import abstractmethod
 from dataclasses import dataclass
-from typing import TYPE_CHECKING, ClassVar, final
+from typing import ClassVar, final
 
 import pyarrow as pa
 from vgi_rpc import ArrowSerializableDataclass
+from vgi_rpc.rpc import OutputCollector
 
 from vgi.invocation import BindResponse
 from vgi.table_function import (
@@ -46,10 +47,7 @@
     init_single_worker,
 )
 
-if TYPE_CHECKING:
-    from vgi_rpc.rpc import OutputCollector
-
-__all__ = ["CopyFromFunction"]
+__all__ = ["CopyFromFunction", "OutputCollector"]
 
 
 @dataclass(kw_only=True)

vgi/table_buffering_function.py

@@ -54,6 +54,7 @@
     pass
 
 __all__ = [
+    "OutputCollector",
     "TableBufferingFunction",
     "TableBufferingParams",
 ]

vgi/table_in_out_function.py

@@ -35,6 +35,7 @@
     pass
 
 __all__ = [
+    "OutputCollector",
     "TableInOutGenerator",
     "TableInOutFunction",
     "TableInOutFunctionStateNoOp",