重构: GetAnonymous/GetSystemUser 改为指向 req/userx 的别名

实现搬到了 req/userx（详见 req 仓库对应提交），这里不再自己维护一份，
避免和 req 互相依赖导致 go.mod 只能靠指向本地兄弟目录的 replace 绕开
版本解析。

顺带清理 go.mod：condition/db/reflux/req 都不再需要 replace，锁定成各自
的真实版本号。

go.mod

@@ -1,32 +1,26 @@
 module git.fsdpf.net/go/contracts
 
-go 1.24
-
-toolchain go1.24.10
-
-replace (
-	git.fsdpf.net/go/condition => ../condition-v2
-	git.fsdpf.net/go/db => ../db-v2
-	git.fsdpf.net/go/reflux => ../reflux
-	git.fsdpf.net/go/req => ../req-v2
-)
+go 1.25.5
 
 require (
-	git.fsdpf.net/go/condition v0.0.0-00010101000000-000000000000
-	git.fsdpf.net/go/db v0.0.0-00010101000000-000000000000
-	git.fsdpf.net/go/reflux v0.0.0-00010101000000-000000000000
-	git.fsdpf.net/go/req v0.0.0-00010101000000-000000000000
+	git.fsdpf.net/go/condition v0.0.0-20241126093638-50e1b3630e6b
+	git.fsdpf.net/go/db v0.0.0-20260820090948-9c6bb5a83508
+	git.fsdpf.net/go/reflux v0.0.0-20260820092857-1f48635da3f1
+	git.fsdpf.net/go/req v0.0.0-20260820100114-1d95bf64a2a0
 	git.fsdpf.net/go/utils v0.0.0-20240509025914-c03a9cb48aff
+	github.com/google/jsonschema-go v0.4.3
+	github.com/mark3labs/mcp-go v0.54.1
 	github.com/samber/do/v2 v2.0.0
-	github.com/stretchr/testify v1.11.1
+	github.com/sashabaranov/go-openai v1.41.2
 )
 
 require (
-	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-sql-driver/mysql v1.7.1 // indirect
+	github.com/google/uuid v1.6.0 // indirect
 	github.com/mattn/go-sqlite3 v1.14.42 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/samber/go-type-to-string v1.8.0 // indirect
+	github.com/santhosh-tekuri/jsonschema/v6 v6.0.2 // indirect
+	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 )
 
 require (
@@ -62,7 +56,7 @@ require (
 	github.com/tidwall/sjson v1.2.5 // indirect
 	golang.org/x/crypto v0.38.0 // indirect
 	golang.org/x/net v0.21.0 // indirect
-	golang.org/x/sys v0.33.0 // indirect
+	golang.org/x/sys v0.41.0 // indirect
 	golang.org/x/text v0.25.0 // indirect
 	google.golang.org/genproto v0.0.0-20221227171554-f9683d7f8bef // indirect
 	google.golang.org/grpc v1.52.0