fix(genapi): scope method-param enums per method, dedupe case-colliding enum consts

Bot API update added RichBlockListItem.type values (a/A/i/I/1) that
Pascal-case to identical const idents, and answerGuestQuery's non-enum
'result' param picked up answerChatJoinRequestQuery's Result enum via
the shared parent="" enum-plan key.

- key method params as method:<name> in the enum plan byField map
- enumDecl.ConstName resolves case collisions with Lower/Upper prefix
- regenerate api/ from 2026-06-11 snapshot

cmd/genapi/enums_collision_test.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/lukaszraczylo/go-telegram/internal/spec"
+	"github.com/stretchr/testify/require"
+)
+
+// Regression: Bot API 9.x RichBlockListItem.type enumerates "a"/"A"/"i"/"I"/"1",
+// which Pascal-case to the same identifier. ConstName must disambiguate.
+func TestEnumDecl_ConstName_CaseCollision(t *testing.T) {
+	d := enumDecl{Name: "RichBlockListItemType", Values: []string{"a", "A", "i", "I", "1"}}
+	got := map[string]bool{}
+	for _, v := range d.Values {
+		n := d.ConstName(v)
+		require.False(t, got[n], "duplicate const ident %q for value %q", n, v)
+		got[n] = true
+	}
+	require.Equal(t, "RichBlockListItemTypeLowerA", d.ConstName("a"))
+	require.Equal(t, "RichBlockListItemTypeUpperA", d.ConstName("A"))
+	// Non-colliding values keep the plain name.
+	require.Equal(t, "RichBlockListItemType1", d.ConstName("1"))
+}
+
+// Regression: answerChatJoinRequestQuery has an enum param named "result";
+// answerGuestQuery has a NON-enum param also named "result". The enum plan
+// must scope method params per method so the enum never leaks onto the
+// other method's field.
+func TestPlanEnums_MethodParamsScopedPerMethod(t *testing.T) {
+	api := &spec.API{
+		Methods: []spec.MethodDecl{
+			{
+				Name: "answerChatJoinRequestQuery",
+				Params: []spec.Field{{
+					Name: "Result", JSONName: "result", Required: true,
+					Type:       spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"},
+					EnumValues: []string{"approve", "decline", "queue"},
+				}},
+			},
+			{
+				Name: "answerGuestQuery",
+				Params: []spec.Field{{
+					Name: "Result", JSONName: "result", Required: true,
+					Type: spec.TypeRef{Kind: spec.KindNamed, Name: "InlineQueryResult"},
+				}},
+			},
+		},
+	}
+	plan := planEnums(api)
+	require.Equal(t, "Result",
+		plan.FieldEnum(methodEnumParent("answerChatJoinRequestQuery"), "Result"))
+	require.Empty(t,
+		plan.FieldEnum(methodEnumParent("answerGuestQuery"), "Result"),
+		"non-enum param must not inherit another method's enum")
+}