#1285 Require plain bullets for checklists on both update-jira-ticket paths

[williamthorsen]

What

Refines the guidance in update-jira-ticket to work around Jira's poor handling of checklist items. Agents are instructed to replace checklist items with plain bullets when submitting Markdown and with plain <li> elements when submitting HTML.

Why

Acceptance criteria forwarded to Jira arrived as bullets reading \[ \] ..., and the escaped brackets stayed in the ticket whenever nobody reread the description after the update. design-and-plan and create-ticket both template acceptance criteria as checkboxes, so the defect reached any ticket whose artefact was forwarded as written rather than being an occasional slip of hand-authored prose.

Details

🐛 Bug fixes

• The Markdown path gains a step directing conversion of task-list syntax to plain - bullets, naming artefact-sourced content as in scope and closing with the carve-out that a checklist does not justify contentFormat: "adf". That closing clause resolves a tension with the path's existing step 2, which reserves ADF for fidelity Markdown cannot express, a description task lists fit.
• The HTML path's conversion step gains a clause prescribing a plain <li>, and the antipattern list names carrying the brackets through as literal text.
• The rule lives in the guidance rather than in the pre-flight checker, whose every rule maps to a documented INVALID_INPUT trigger; bracket text triggers none.

Closes #1285

[github-actions]

Dependency audit

Production dependency audit passed.