Update Playbooks v2.6 checklists documentation

[cwarnermm]

Updates Mattermost Product Documentation to reflect Playbooks v2.6.0 checklist workflow changes and mobile v2.35.0 updates.

Changes:

• Channel checklists as first-class workflows for public/private channels
• Channel-based permissions model

Closes #8654

Generated with Claude Code

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[cwarnermm]

I'd appreciate help with answers to the following questions as part of this docs lift:

1. Are there checklist permissions details to call out -- specifically around guest access: can they create checklists if they have channel post permissions?
2. Can a single channel have both playbook runs and channel checklists? Anything worth noting when both are present, if supported?
3. What happens if a user loses channel access while actively working on a checklist?
4. What happens when a channel is archived? Are those checklists available/accessible? What if the channel is unarchived?
5. Are checklists backed up as part of channel data?
6. Is it possible for multiple users to edit the same checklist task at the same time? Who wins? Are there safeguards in place against conflicting edits?
7. Are users notified of checklist updates?
8. Is there a maximum number or upper limit to the number of checklists for a given channel?

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Newest code from mattermost has been published to preview environment for Git SHA fecf375

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[jgheithcock]

I'd appreciate help with answers to the following questions as part of this docs lift:

1. Are there checklist permissions details to call out -- specifically around guest access: can they create checklists if they have channel post permissions?
2. Can a single channel have both playbook runs and channel checklists? Anything worth noting when both are present, if supported?
3. What happens if a user loses channel access while actively working on a checklist?
4. What happens when a channel is archived? Are those checklists available/accessible? What if the channel is unarchived?
5. Are checklists backed up as part of channel data?
6. Is it possible for multiple users to edit the same checklist task at the same time? Who wins? Are there safeguards in place against conflicting edits?
7. Are users notified of checklist updates?
8. Is there a maximum number or upper limit to the number of checklists for a given channel?

Claude reports the following (and I've vetted it and made some parenthetical comments below - @calebroseland & @JulienTant -tagging you in to vet my vetting ;-) ):
• Guest Access: Guest users can create and manage channel checklists if they have posting permissions in the channel, but cannot access checklists from private channels they don't belong to.

• Coexistence: A single channel can contain both playbook runs and standalone channel checklists simultaneously - channel members have immediate edit access to checklists but must opt-in to become participants before editing playbook runs.

• Losing Channel Access: Users who lose channel membership immediately lose all access to that channel's checklists, and any unsaved changes are lost.

• Channel Archival: Checklists in archived channels become read-only (viewable but not editable) and regain full functionality when the channel is unarchived. (Note that, as there was no playbook, the playbook actions that run when a playbook is restarted do not exist.)

• Backup: Channel checklists are stored in the Mattermost database and included in standard database backups with no separate backup mechanism. (I really don't think this needs to be documented as it is just what is true across the board.)

• Concurrent Editing: Multiple users can edit the same checklist simultaneously with no conflict resolution - the last save wins and users may overwrite each other's changes.

• Notifications: Users receive real-time WebSocket updates when checklists are modified, but there are no specific notification preferences for checklist activities.

• Limits: No limits exist on number of checklists per channel or tasks per checklist, but individual task descriptions are limited to 4,000 characters.