chore: update Go toolchain to 1.27.0

[fenio]

Summary

• set the module Go directive to 1.27.0
• set the golangci-lint target to 1.27.0
• keep build and test workflows aligned on their existing 1.27.0 toolchain
• manage Actions and Go CodeQL analysis in a repository workflow that explicitly installs Go 1.27
• remove stale module checksums via Go 1.27 go mod tidy

GitHub default CodeQL setup has been disabled because its hosted Go 1.26 toolchain cannot analyze a Go 1.27 module. Both Actions and Go analysis are now defined in .github/workflows/codeql.yml.

Verification

• go test -count=1 ./...
• go run golang.org/x/vuln/cmd/govulncheck@v1.7.0 ./...
• golangci-lint run --no-config
• actionlint .github/workflows/build.yaml .github/workflows/test.yaml .github/workflows/codeql.yml
• go mod verify

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.56%. Comparing base (1b6ff0c) to head (d89ecef).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #442   +/-   ##
=======================================
  Coverage   50.56%   50.56%           
=======================================
  Files          20       20           
  Lines         973      973           
=======================================
  Hits          492      492           
  Misses        481      481           

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