chore: drop core replace from root go.mod

Remove `replace github.com/evstack/ev-node/core => ./core` so the
published module resolves core v1.1.0 from the proxy with a proper
go.sum checksum, instead of relying on a local path that consumers
ignore. Local cross-module dev is handled by go.work (go.work.example
already `use`s ./core).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: tac0turtle

go.mod

@@ -51,8 +51,6 @@ require (
 	gotest.tools/v3 v3.5.2
 )
 
-replace github.com/evstack/ev-node/core => ./core
-
 require (
 	cloud.google.com/go v0.123.0 // indirect
 	cloud.google.com/go/auth v0.20.0 // indirect

go.sum

@@ -188,6 +188,8 @@ github.com/envoyproxy/go-control-plane/envoy v1.37.0/go.mod h1:DReE9MMrmecPy+YvQ
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
 github.com/envoyproxy/protoc-gen-validate v1.3.3 h1:MVQghNeW+LZcmXe7SY1V36Z+WFMDjpqGAGacLe2T0ds=
 github.com/envoyproxy/protoc-gen-validate v1.3.3/go.mod h1:TsndJ/ngyIdQRhMcVVGDDHINPLWB7C82oDArY51KfB0=
+github.com/evstack/ev-node/core v1.1.0 h1:Sa7uU5yuNF7YUyLBHPThD6Jt8/jacM1epRLATrdvKRE=
+github.com/evstack/ev-node/core v1.1.0/go.mod h1:n2w/LhYQTPsi48m6lMj16YiIqsaQw6gxwjyJvR+B3sY=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
 github.com/fatih/color v1.13.0/go.mod h1:kLAiJbzzSOZDVNGyDpeOxJ47H46qBXwg5ILebYFFOfk=
 github.com/fatih/color v1.18.0 h1:S8gINlzdQ840/4pfAwic/ZE0djQEH3wM94VfqLTZcOM=