Allow nested routes sharing the same path parameter matcher

When two routes share the same parameter at the same node position
(e.g. GET /restaurants/${id} and GET /restaurants/${id}/menu),
reuse the existing equivalent matcher instead of raising a conflict.
Non-equivalent matchers (different names, kinds, or glob patterns)
at the same node for the same method still raise ValueError.

packages/kaya-core/tests/test_asgi.py

@@ -190,3 +190,29 @@ class AsgiTest(unittest.TestCase):
                 'employee_id': 101325
             }, response)
 
+    @async_test
+    async def test_nested_param_routes(self):
+        app = KayaApp()
+
+        @app.GET('/restaurants/${id}')
+        async def restaurant(ctx: HttpContext, id: str) -> None:
+            await ctx.send_str(200, f"restaurant:{id}")
+
+        @app.GET('/restaurants/${id}/menu')
+        async def menu(ctx: HttpContext, id: str) -> None:
+            await ctx.send_str(200, f"menu:{id}")
+
+        transport = httpx.ASGITransport(app=app)
+
+        async with httpx.AsyncClient(transport=transport, base_url="http://127.0.0.1:80") as client:
+            r = await client.get("/restaurants/42")
+            self.assertEqual(200, r.status_code)
+            self.assertEqual("restaurant:42", r.text)
+
+            r = await client.get("/restaurants/42/menu")
+            self.assertEqual(200, r.status_code)
+            self.assertEqual("menu:42", r.text)
+
+            r = await client.get("/restaurants/42/unknown")
+            self.assertEqual(404, r.status_code)
+