🧹 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.

Refs PCC-544

[greptile-apps]

Greptile Summary

The PR consistently upgrades the Dagger engine from 0.21.7 to 0.21.8 and dagger/dagger-for-github from v8.2.0 to v8.4.1.

• Updates Dagger installation and invocation steps across CI, pull-request, nightly, and release workflows.
• Aligns dagger.json with the workflow engine version.

Confidence Score: 5/5

The PR appears safe to merge with no actionable compatibility or synchronization defects identified.

The engine and GitHub Action versions are updated consistently, and the changed versions continue to support the repository’s existing Dagger APIs and workflow input patterns.

Important Files Changed

Filename	Overview
.github/workflows/ci.yaml	Updates both Dagger action usages and the shared engine version without changing workflow behavior or inputs.
.github/workflows/cut-release.yaml	Updates the release-cutting workflow to the new action and matching engine version.
.github/workflows/nightly.yaml	Updates the nightly workflow installation action and engine version consistently.
.github/workflows/pr.yaml	Updates both conditional and unconditional Dagger installation steps with compatible versions.
.github/workflows/release.yaml	Updates the published-release workflow to the new action and matching engine version.
dagger.json	Pins the Dagger module engine to v0.21.8, consistent with every changed workflow.

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

[linear-code]

PCC-544