chore: bump Dagger to 0.21.8

[jpmcb]

Bump Dagger engine to v0.21.8 (latest, 2026-07-29) and dagger/dagger-for-github to v8.4.1.

[greptile-apps]

Greptile Summary

This PR aligns the repository’s Dagger engine declarations and CI installation with Dagger 0.21.8 and upgrades dagger-for-github to v8.4.1.

• Updates the Dagger CLI version and GitHub Action in the Go and pull-request workflows.
• Updates all eight module manifests to require engine version v0.21.8.

Confidence Score: 5/5

The PR appears safe to merge, with the workflow-installed Dagger version and module engine requirements consistently aligned at v0.21.8.

No concrete build, runtime, compatibility, or security failure caused by the version updates was established.

Important Files Changed

Filename	Overview
.github/workflows/go.yaml	Updates the CI-installed Dagger CLI and action versions consistently, with no concrete workflow regression identified.
.github/workflows/pr.yaml	Applies the same Dagger CLI and action upgrade to both Dagger-backed pull-request checks.
bucketupload/dagger.json	Updates the module’s engine requirement from v0.20.8 to v0.21.8.
checksum/dagger.json	Updates the module’s engine requirement from v0.20.8 to v0.21.8.
dockerimage/dagger.json	Updates the module’s engine requirement from v0.21.7 to v0.21.8.
ghcontrib/dagger.json	Updates the module’s engine requirement from v0.20.8 to v0.21.8.
ghrelease/dagger.json	Updates the module’s engine requirement from v0.20.8 to v0.21.8.
go/dagger.json	Updates the module’s engine requirement from v0.20.8 to v0.21.8.
golangcilint/dagger.json	Updates the module’s engine requirement from v0.20.8 to v0.21.8.
utils/dagger.json	Updates the module’s engine requirement from v0.20.8 to v0.21.8.

_{Reviews (1): Last reviewed commit: "chore: bump Dagger to 0.21.8" | Re-trigger Greptile}