Read the IGC version compute-runtime pins, instead of taking the newest

[MickLesk]

✍️ Description

intel-opencl-icd depends on one exact intel-igc-opencl-2, and _resolve_igc_tag was meant to read that version from compute-runtime's release notes. It never did: TOOLS_GH_REL_JSON holds a list when the release was fetched as latest, jq cannot index an array with .body, and the error was swallowed — so the tag silently stayed latest.

That matched by luck until IGC 2.41.5 appeared on 10 September while 26.31.39395.13 still pins 2.40.13:

intel-opencl-icd : Depends: intel-igc-opencl-2 (< 2.40.13+~) but 2.41.5 is to be installed

Unresolved now means empty, and the caller skips OpenCL with a warning rather than installing a pair dpkg will reject. VA-API is unaffected.

🔗 Related Issue

Fixes # Discord

✅ Prerequisites (X in brackets)

• Self-review completed – Code follows project standards.
• Tested thoroughly – Changes work as expected (Proxmox VE and/or Incus, as applicable).
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.
• API.txt regenerated – If a function signature or behavior changed, API.txt was updated to match.

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🛠️ Type of Change (X in brackets)

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing behavior in a way that may require updates in every downstream script.
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, docs/, CONTRIBUTING.md, or other docs.

[github-actions]

Try this branch

The engine and the scripts resolve independently, so a production script can
be run against the engine from this PR by setting one variable:

COMMUNITY_SCRIPTS_CORE_URL=https://raw.githubusercontent.com/community-scripts/core/fix/igc-pin \
bash -c "$(curl -fsSL https://raw.githubusercontent.com/community-scripts/ProxmoxVED/main/ct/debian.sh)"

Swap ct/debian.sh for whatever exercises the change.

Run a script from a fork as well

curl -fsSL https://raw.githubusercontent.com/community-scripts/core/fix/igc-pin/tools/run.sh |
  bash -s -- https://raw.githubusercontent.com/YOU/ProxmoxVED/your-branch ct/debian.sh \
             https://raw.githubusercontent.com/community-scripts/core/fix/igc-pin

Note that run.sh is reached through a pipe, so the script it starts inherits
an exhausted stdin. Whiptail is fine — it opens /dev/tty — but a plain read
would see EOF. The single-variable form above does not have that problem.

Useful flags while testing

dev_mode=net logs every engine fetch with status and duration, which is the
quickest way to confirm the branch is really being used. dev_mode=keep stops a
failed build from deleting the container along with the evidence.