Title-case documentation headings and clarify experiment output

[RulaHallak]

Summary

• Title-case the DSE subsection headings in doc/USER_GUIDE.rst (DSE Parameter Exclusions and Metric Errors and Report Strategies) so they match the surrounding heading style.
• Title-case the unified experiment output headings in doc/reporting.rst and clarify how experiment.json records the system name, Standalone and Slurm runs, unknown status, and metrics.
• The Sphinx html_static_path and html_css_files lines were added and then removed, so doc/conf.py is not in the diff.
• This branch also contains upstream commit 659ade63 (ci: give the Coverity scan enough CPU and memory to run in parallel), which changes .ci/pipeline/coverity_matrix.yaml. That commit is not on fork main.

Test Plan

• Working tree on docs/v180-updates is clean and matches origin/docs/v180-updates.
• Compared this branch with fork main using git diff origin/main...HEAD. The net change is:
  • doc/USER_GUIDE.rst (4 lines)
  • doc/reporting.rst (14 lines)
  • .ci/pipeline/coverity_matrix.yaml (10 lines)
• git diff --check reported no whitespace errors on the documentation commits.
• Built the HTML documentation on this branch before the stylesheet lines were added, and those lines have since been removed:

  uv sync --extra docs
  uv run sphinx-build -M html doc doc/_build
  

  Sphinx v8.2.3 finished with build succeeded and no warnings.
• The Coverity pipeline change was not executed locally.

Additional Notes

• Opened as a draft.
• The same documentation branch is proposed upstream in Title-case documentation headings and clarify experiment output NVIDIA/cloudai#1089.