test: make the suite run under Windows

Windows spells a path with backslashes, and three fixtures took the POSIX shape: a config value written into a TOML basic string read `C:\users\…` as an escape, tool arguments built with an f-string broke the same way, and a root was compared as `str(path)` against `/srv/skills`. Paths are encoded with `json.dumps` (whose escaping is valid TOML and valid JSON) and compared as `Path` objects, so the same root matches in either spelling.

`test_interrupt.py` delivers SIGINT with `os.kill(pid, SIGINT)`, which is `TerminateProcess` on Windows, and the router itself needs `add_signal_handler`: the module is skipped there.

`python scripts/wine_pdm.py ci` is green: ruff, basedpyright 0 errors, 1156 passed / 30 skipped.

tests/test_skills/test_discovery.py

@@ -1,13 +1,10 @@
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from pathlib import Path
 
 from plyngent.config.models import SkillsConfig
 from plyngent.skills import SKILL_FILE, Skill, SkillStore, build_roots, validate_skill_name
 
-if TYPE_CHECKING:
-    from pathlib import Path
-
 
 def _write_skill(root: Path, name: str, *, description: str | None = "A test skill", body: str = "Body.") -> Path:
     directory = root / name
@@ -28,12 +25,13 @@ def test_build_roots_orders_explicit_paths_first(tmp_path: Path) -> None:
         user_config_dir=tmp_path / "config",
         home=tmp_path / "home",
     )
-    assert [(r.origin, r.scope, str(r.path)) for r in roots] == [
-        ("config", "user", str(tmp_path / "home" / "team-skills")),
-        ("config", "user", "/srv/skills"),
-        ("plyngent", "user", str(tmp_path / "config" / "skills")),
-        ("claude", "user", str(tmp_path / "home" / ".claude" / "skills")),
-        ("claude", "project", str(tmp_path / "proj" / ".claude" / "skills")),
+    # Paths, not strings: a Windows run spells the same root differently.
+    assert [(r.origin, r.scope, r.path) for r in roots] == [
+        ("config", "user", tmp_path / "home" / "team-skills"),
+        ("config", "user", Path("/srv/skills")),
+        ("plyngent", "user", tmp_path / "config" / "skills"),
+        ("claude", "user", tmp_path / "home" / ".claude" / "skills"),
+        ("claude", "project", tmp_path / "proj" / ".claude" / "skills"),
     ]