fix(security): pin Go toolchain and bump x/sys to clear Grype scan failures

Weekly Security Scan job fails because the compiled binary embeds
go1.26.4, which has two disclosed stdlib vulnerabilities (GO-2026-4970
high, GO-2026-5856 medium). golang.org/x/sys v0.41.0 also carries a
low-severity issue (GO-2026-5024). Pin toolchain to go1.26.5 and bump
x/sys to v0.44.0 to pick up the fixes.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: glageju

go.mod

@@ -2,6 +2,8 @@ module github.com/stackloklabs/yardstick
 
 go 1.26
 
+toolchain go1.26.5
+
 require (
 	github.com/google/jsonschema-go v0.4.3
 	github.com/modelcontextprotocol/go-sdk v1.6.1
@@ -15,6 +17,6 @@ require (
 	github.com/segmentio/encoding v0.5.4 // indirect
 	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 	golang.org/x/oauth2 v0.35.0 // indirect
-	golang.org/x/sys v0.41.0 // indirect
+	golang.org/x/sys v0.44.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -6,8 +6,6 @@ github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/google/jsonschema-go v0.4.3 h1:/DBOLZTfDow7pe2GmaJNhltueGTtDKICi8V8p+DQPd0=
 github.com/google/jsonschema-go v0.4.3/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
-github.com/modelcontextprotocol/go-sdk v1.6.0 h1:PPLS3kn7WtOEnR+Af4X5H96SG0qSab8R/ZQT/HkhPkY=
-github.com/modelcontextprotocol/go-sdk v1.6.0/go.mod h1:kzm3kzFL1/+AziGOE0nUs3gvPoNxMCvkxokMkuFapXQ=
 github.com/modelcontextprotocol/go-sdk v1.6.1 h1:0zOSupjKUxPKSocPT1Wtago+mUHU2/uZ4xSOY0FGReU=
 github.com/modelcontextprotocol/go-sdk v1.6.1/go.mod h1:kzm3kzFL1/+AziGOE0nUs3gvPoNxMCvkxokMkuFapXQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -22,8 +20,8 @@ github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zI
 github.com/yosida95/uritemplate/v3 v3.0.2/go.mod h1:ILOh0sOhIJR3+L/8afwt/kE++YT040gmv5BQTMR2HP4=
 golang.org/x/oauth2 v0.35.0 h1:Mv2mzuHuZuY2+bkyWXIHMfhNdJAdwW3FuWeCPYN5GVQ=
 golang.org/x/oauth2 v0.35.0/go.mod h1:lzm5WQJQwKZ3nwavOZ3IS5Aulzxi68dUSgRHujetwEA=
-golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
-golang.org/x/sys v0.41.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/sys v0.44.0 h1:ildZl3J4uzeKP07r2F++Op7E9B29JRUy+a27EibtBTQ=
+golang.org/x/sys v0.44.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
 golang.org/x/tools v0.42.0 h1:uNgphsn75Tdz5Ji2q36v/nsFSfR/9BRFvqhGBaJGd5k=
 golang.org/x/tools v0.42.0/go.mod h1:Ma6lCIwGZvHK6XtgbswSoWroEkhugApmsXyrUmBhfr0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=