fix(azdo): ship valid Node24 task handlers and restore AzDO test and publish

[Todor Genov (tgenov)]

Refs #444

Problem

The Marketplace extension devcontainers.ci is at 0.3.1900000417 (2025-02-07). Its task uses Node16. This causes the warnings in #444. No publish ran after that date:

• All 12 CI (main) runs on main from 2025-10-16 to 2026-04-16 failed in "Run AzDO test". The release needed that job. The logs have expired, so the root cause is not known.
• Add "Publish the AzDO extension" input #439–Fix conditions #441 then turned off the AzDO test and publish.

A publish of main today would ship two more defects:

1. DevcontainersCi/task.json uses Node20 (Update Node, NPM, Go tools and Debian  #438). The agent has no Node20 handler. The valid keys are Node, Node10, Node16, Node20_1 and Node24 (tasks.schema.json).
2. DevcontainersMerge/task.json uses only Node16. feat: native multi-platform builds via runner matrix (no QEMU emulation) #435 added it by mistake.

Changes

• Both task.json files declare Node24, Node20_1 and Node16. Agents pick Node24 first. Node16 keeps agents older than 3.230.2 working. The agent shows no deprecation warning when Node20_1 or Node24 is present (CheckIfTaskNodeRunnerIsDeprecated).
• merge/action.yml: node20 → node24, the same as action.yml. GitHub deprecated Node 20 for actions.
• ci_common.yml:
  • test-azdo is a job again. checks-succeeded and release do not need it, so an AzDO failure does not stop the GitHub Action release. The run shows the failure.
  • The AzDO publish moves to a new job, publish-azdo. It runs after release, and only if test-azdo passed.

I did not restore the enableAzdo input. Its expression gave true for false.

Before merge (maintainer)

/test uses the workflows from main, not from this PR. To test this change:

1. Push this branch to devcontainers/ci. The AzDO pipeline can build only commits in that repo.
2. Run "CI (branch)" on that branch. Set prNumber to this PR. Without it, IMAGE_TAG is empty and the AzDO test stops.
3. Read the "Run AzDO test" log. publish-azdo does not run, because release is false.

If the log shows a token error, replace AZDO_TOKEN or refresh its access (see CONTRIBUTING.md).

Security

This PR enables test-azdo on /test again. The job runs the PR's code with AZDO_TOKEN, as before #441. pr_auto never runs it. Any repository collaborator can send /test. Read the full diff before you send it.

Verification

• ./scripts/build-local.sh in the dev container (Node 24): passes. 49 tests in common and 2 in the AzDO task pass.
• All handler keys in both task.json files are in the schema. Node20 on main is not.
• actionlint 1.7.7: no new findings.
• Not tested: a real AZDO_TOKEN, the AzDO test pipeline, and DevcontainersMerge in AzDO. The test pipeline does not use that task, so the first publish ships it untested.

Follow-up (not in this PR)

• DevcontainersMerge/task.json stays at 0.0.0. The build sets the patch version for DevcontainersCi only. Agents cache tasks by version, so later changes may not reach them.
• .devcontainer/Dockerfile installs tfx-cli with no version.

[Todor Genov (tgenov)]

@copilot review this PR