chore: align proof/toolchain versions and CI refs

[davidahmann]

Summary

• align dependency and tooling versions across local/CI/release paths
• update Go command surfaces that were tied to pre-upgrade assumptions
• keep CI/release workflow references consistent with current branch and module state

Changes

• updated module constraints and sums in go.mod / go.sum
• adjusted CI/release workflow definitions in .github/workflows/ci.yml and .github/workflows/release.yml
• refreshed build/test targets in Makefile
• applied compatibility fixes in:
  • cmd/gait/mcp.go
  • cmd/gait/mcp_server.go
  • cmd/gait/migrate.go
  • core/fsx/fsx.go
  • core/projectconfig/config.go
  • core/registry/install.go
  • core/regress/init.go
  • core/ui/runner.go

Validation

• gait doctor --json
• make prepush-full
• push hook make prepush