ui: fix versions page showing 'No Changes' on initial SPA navigation

[nh2]

Description

The Nomad UI was bugged: It would not show job diffs on first load when doing navigation to Versions inside the SPA.

See commit message for more details.

I tested this change against Nomad v1.11.3 only.

One needs to run make dev-ui to regenerate command/agent/bindata_assetfs.go to test this change.

Testing & Reproduction steps

Note I let an LLM generate these for me (as I ran the entire multi-hour original investigation with it) and then used them as my repro (so they work):

Details

Prerequisites: A running Nomad cluster (even nomad agent -dev suffices).

Setup — create a job with 2 versions:

# Submit Version #0 (count=3)
cat <<'EOF' | curl -s -X PUT "http://localhost:4646/v1/jobs" -d @-
{
  "Job": {
    "ID": "test-versions-diff",
    "Name": "test-versions-diff",
    "Type": "batch",
    "Datacenters": ["dc1"],
    "TaskGroups": [{
      "Name": "main",
      "Count": 3,
      "Tasks": [{
        "Name": "sleep",
        "Driver": "raw_exec",
        "Config": { "command": "/bin/sleep", "args": ["300"] },
        "Resources": { "CPU": 100, "MemoryMB": 64 }
      }]
    }]
  }
}
EOF

# Submit Version #1 (count=1) — creates a diff (Count: 3 -> 1)
cat <<'EOF' | curl -s -X PUT "http://localhost:4646/v1/jobs" -d @-
{
  "Job": {
    "ID": "test-versions-diff",
    "Name": "test-versions-diff",
    "Type": "batch",
    "Datacenters": ["dc1"],
    "TaskGroups": [{
      "Name": "main",
      "Count": 1,
      "Tasks": [{
        "Name": "sleep",
        "Driver": "raw_exec",
        "Config": { "command": "/bin/sleep", "args": ["300"] },
        "Resources": { "CPU": 100, "MemoryMB": 64 }
      }]
    }]
  }
}
EOF

Verify the API returns a diff:

curl -s "http://localhost:4646/v1/job/test-versions-diff/versions?diffs=true" | jq '.Diffs | length'
# Should output: 1

Reproduce the bug (before fix):

1. Close all Nomad UI browser tabs (this resets the in-memory watchList service).
2. Open the job's Overview page: http://localhost:4646/ui/jobs/test-versions-diff
3. Wait for the page to fully load.
4. Click the "Versions" tab (SPA navigation — do NOT open it in a new tab or hard-refresh).
5. Observe: Version Pass agent configuration into fingerprinter #1 shows "No Changes" despite the API having a valid diff.

Verify the fix (after fix):

Repeat steps 1-4 above. Version #1 should now show "See 1 Change" with the correct diff (Count: 3 -> 1).

Root cause: {{did-update this.versionsDidUpdate this.job.versions}} only fires when this.job.versions changes after the template's initial render. On SPA navigation from Overview to Versions, the versions are already loaded and cached at the current blocking-query index, so did-update never fires, versionsDidUpdate() is never called, and diffs are never fetched. Adding {{did-insert this.versionsDidUpdate}} ensures diffs are fetched on initial render of the Versions page.

Contributor Checklist

• Changelog Entry If this PR changes user-facing behavior, please generate and add a
  changelog entry using the make cl command.
• Testing Please add tests to cover any new functionality or to demonstrate bug fixes and
  ensure regressions will be caught.
• Documentation If the change impacts user-facing functionality such as the CLI, API, UI,
  and job configuration, please update the Nomad product documentation, which is stored in the
  web-unified-docs repo. Refer to the web-unified-docs contributor guide for docs guidelines.
  Please also consider whether the change requires notes within the upgrade
  guide. If you would like help with the docs, tag the nomad-docs team in this PR.

Reviewer Checklist

• Backport Labels Please add the correct backport labels as described by the internal
  backporting document.
• Commit Type Ensure the correct merge method is selected which should be "squash and merge"
  in the majority of situations. The main exceptions are long-lived feature branches or merges where
  history should be preserved.
• Enterprise PRs If this is an enterprise only PR, please add any required changelog entry
  within the public repository.

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.