perf: integrate go-sdk schema caching optimization (Phase 1)

Add replace directive to use github.com/SamMorrowDrums/go-sdk fork
with schema caching optimization for improved tool registration performance.

Expected improvements:
- 132x faster tool registration
- 51x fewer allocations
- 19% faster per-tool-call validation

Co-authored-by: SamMorrowDrums <4811358+SamMorrowDrums@users.noreply.github.com>

Author: Copilot

go.mod

@@ -2,6 +2,8 @@ module github.com/github/github-mcp-server
 
 go 1.24.0
 
+replace github.com/modelcontextprotocol/go-sdk => github.com/SamMorrowDrums/go-sdk v0.0.0-20251204132233-46310a70a79a
+
 require (
 	github.com/google/go-github/v79 v79.0.0
 	github.com/google/jsonschema-go v0.3.0

go.sum

@@ -1,3 +1,5 @@
+github.com/SamMorrowDrums/go-sdk v0.0.0-20251204132233-46310a70a79a h1:LxbkoIMLsGVBsRYrDCcB06Q1Ciltx6b2M3OxTl6T7kI=
+github.com/SamMorrowDrums/go-sdk v0.0.0-20251204132233-46310a70a79a/go.mod h1:6fM3LCm3yV7pAs8isnKLn07oKtB0MP9LHd3DfAcKw10=
 github.com/aymerick/douceur v0.2.0 h1:Mv+mAeH1Q+n9Fr+oyamOlAkUNPWPlA8PPGR0QAaYuPk=
 github.com/aymerick/douceur v0.2.0/go.mod h1:wlT5vV2O3h55X9m7iVYN0TBM0NH/MmbLnd30/FjWUq4=
 github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
@@ -55,8 +57,6 @@ github.com/microcosm-cc/bluemonday v1.0.27 h1:MpEUotklkwCSLeH+Qdx1VJgNqLlpY2KXwX
 github.com/microcosm-cc/bluemonday v1.0.27/go.mod h1:jFi9vgW+H7c3V0lb6nR74Ib/DIB5OBs92Dimizgw2cA=
 github.com/migueleliasweb/go-github-mock v1.3.0 h1:2sVP9JEMB2ubQw1IKto3/fzF51oFC6eVWOOFDgQoq88=
 github.com/migueleliasweb/go-github-mock v1.3.0/go.mod h1:ipQhV8fTcj/G6m7BKzin08GaJ/3B5/SonRAkgrk0zCY=
-github.com/modelcontextprotocol/go-sdk v1.1.0 h1:Qjayg53dnKC4UZ+792W21e4BpwEZBzwgRW6LrjLWSwA=
-github.com/modelcontextprotocol/go-sdk v1.1.0/go.mod h1:6fM3LCm3yV7pAs8isnKLn07oKtB0MP9LHd3DfAcKw10=
 github.com/muesli/cache2go v0.0.0-20221011235721-518229cd8021 h1:31Y+Yu373ymebRdJN1cWLLooHH8xAr0MhKTEJGV/87g=
 github.com/muesli/cache2go v0.0.0-20221011235721-518229cd8021/go.mod h1:WERUkUryfUWlrHnFSO/BEUZ+7Ns8aZy7iVOGewxKzcc=
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=