fix(lint): point main's exempt-pair test at the repo root

`test_every_exempt_pair_still_exists` (added on main, #177) joined each
_TYPER_COMMANDS entry onto src/coder_eval. 1/8 made those keys repo-relative
because the gate now reports repo-relative paths for two roots, so the join
produced src/coder_eval/src/coder_eval/... and the test failed after the
rebase. It resolves against the repo root instead; what it guards is
unchanged.

A silent conflict: both sides merged textually, and only the test run showed it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: uipreliga

tests/test_prose_budget.py

@@ -103,9 +103,9 @@ def test_every_exempt_pair_still_exists(self) -> None:
         failure CE057's membership test exists to catch."""
         import ast
 
-        package = Path(__file__).resolve().parents[1] / "src" / "coder_eval"
+        repo_root = Path(__file__).resolve().parents[1]
         for rel, name in sorted(prose_budget._TYPER_COMMANDS):
-            path = package / rel
+            path = repo_root / rel
             assert path.is_file(), f"_TYPER_COMMANDS names {rel}, which does not exist"
             tree = ast.parse(path.read_text(encoding="utf-8"))
             top_level = {node.name for node in tree.body if isinstance(node, ast.FunctionDef | ast.AsyncFunctionDef)}