[zzwong]

Summary

• Select Go 1.27.4 for development and builds via the toolchain directive, retaining the existing Go language minimum and dependency graph.

Validation

• Reviewed compiler selectors and shared workflow/action sources.
• Parsed changed YAML/TOML and checked toolchain pins, unchanged language directives, and narrow diffs.
• Build, test, lint, and tidy were not run locally because this environment has no Go compiler. CI must validate the new compiler before merge.
• No release, merge, auto-merge, or deployment performed. Existing published binaries are not rebuilt by this draft PR.

Shared linter compatibility

Initial CI confirmed Go 1.27.4, but the shared golangci-lint v2.12.2 binary was built with Go 1.26 and cannot analyze the new compiler's packages. Pin only the go-lint action to b816e09a862eec83f6ff334f94d6b96894f405ad from open-cli-collective/.github#54, which upgrades the linter to v2.15.0. All lint checks remain enabled. The shared action change should be reviewed alongside this PR; no floating tag was moved. CI is rerunning automatically for the updated commit.