Fix text-auditor copy drift in triage prompts and scripts

[github-actions]

Summary

This PR implements all text fixes requested in issue #1822:

1. Updated pr-existing-comments.sh usage text to match actual default behavior (truncated text unless --full is passed).
2. Updated scripts/trigger-ci-workflows.sh unknown-argument hint to include --help.
3. Fixed the comma splice in the "bury the lede" guidance in both issue-triage variants:
   • claude-workflows/issue-triage/ro/action.yml
   • claude-workflows/issue-triage/rwx/action.yml
4. Fixed the comma splice in the recommendation example sentence in both issue-triage variants.

Validation

• Shell syntax checks passed for:
  • claude-workflows/pr-review/scripts/pr-existing-comments.sh
  • scripts/trigger-ci-workflows.sh
• Composite action validation passed (make lint-actions).

Resolves #1822.

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What is this? | From workflow: Trigger Text Auditor

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