ci: complete the JetBrains test container

[markijbema]

What

• Bake FreeType, Fontconfig, and DejaVu fonts into the JetBrains CI image so JBR-based Swing tests can run without installing OS packages in each job.
• Encode the Gradle wrapper distribution URL hash in base 36, matching Gradle's cache directory algorithm, instead of using the hexadecimal MD5 digest.
• Prewarm Bun's global package cache in an intermediate build stage, then copy only that cache into the final image.

Why

The current image contains Bun and Java but is missing the font stack required by JetBrains Runtime's libfontmanager.so. The test workflow currently works around that with apt-get update and package installation on every run.

The image also places the pre-downloaded Gradle distribution under the wrong cache directory because Gradle uses BigInteger(md5).toString(36). Correcting the hash lets the wrapper consume the distribution already baked into the image.

Prewarming BUN_INSTALL_CACHE_DIR avoids downloading unchanged packages during CI. The workflow still runs bun install, so each PR validates its current lockfile and materializes an exact node_modules; only missing or newer packages need downloading. Source files and node_modules from the image build stay in the intermediate stage and are not copied into the runtime image.

After this merges and containers.yml publishes ghcr.io/kilo-org/build/jetbrains:24.04, #11342 can remove its temporary APT step while retaining bun install.

Built for Mark IJbema by Kilo for Slack

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• packages/containers/README.md
• packages/containers/jetbrains/Dockerfile

Previous Review Summaries (2 snapshots, latest commit 57b7177)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit 57b7177)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• packages/containers/README.md
• packages/containers/jetbrains/Dockerfile

Previous review (commit 9dd4711)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (1 file)

• packages/containers/jetbrains/Dockerfile

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_{Review guidance: REVIEW.md from base branch main}