Document truncated failure details and -MaxJobs parameter in tips (#5)

* Add notes on XHarness and artifact handling

* Refine tips based on multi-model review

- XHarness: Use correct Helix work items API endpoint, note as script gap
- Truncated details: Document existing totalFailedJobs/failedJobNames fields
  and -MaxJobs parameter instead of grep workaround
- Drop Container artifact tip (belongs as script enhancement, not documentation)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Keep only generic tip, drop MAUI-specific content

- Remove XHarness exit-0 tip (MAUI-specific config, not general XHarness behavior)
- Remove 'UITest jobs' reference from truncated details tip

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: PureWeen

plugins/dotnet-dnceng/skills/ci-analysis/SKILL.md

@@ -136,3 +136,4 @@ Lead with a 1-2 sentence verdict, then the summary table, then detail bullets (o
 3. Use `-SearchMihuBot` for semantic search of related issues
 4. `gh pr checks --json` fields: `bucket`, `completedAt`, `description`, `event`, `link`, `name`, `startedAt`, `state`, `workflow` — `state` has `SUCCESS`/`FAILURE` directly (no `conclusion` field)
 5. "Canceled" ≠ "Failed" — canceled jobs may have recoverable Helix results. Helix data may persist even when AzDO builds have expired — query Helix directly if you have job IDs.
+6. **Truncated failure details**: When `failedJobDetailsTruncated` is `true` in the JSON output, the `failedJobDetails` array is capped at `-MaxJobs` (default 5). The full failure count is always available in `totalFailedJobs`, and all failed job names are listed in `failedJobNames` — use these to assess the full scope before investigating details. Pass `-MaxJobs N` to increase the detail cap for builds with many failures.