[Improve] List Discord Add Reactions as a required install permission

[roomote-roomote]

Opened on behalf of Matt Rubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Discord.

What changed

Discord bot setup copy and public docs list Add Reactions as a required installation permission. Channel diagnostics now enforce the same: add_reactions is part of requiredPermissions, so a channel without that permission is reported unusable (canUseChannel: false).

Why this change was made

Operators were getting soft optional reaction-permission guidance while install requested Add Reactions, and diagnostics still accepted reaction-denied channels as usable. Review feedback asked to align enforcement with the required-permission wording.

Impact

• Setup/docs and install permissions language match runtime channel checks
• Selecting a default Discord channel (or other diagnose-backed flows) fails closed when Add Reactions is missing
• Denied reaction permission surfaces as missingPermissions: ['add_reactions']

Screenshots

[roomote-roomote]

No new code issues found. See task

• apps/docs/providers/communications/discord.mdx:43-50 and apps/web/src/app/(onboarding)/setup/ProviderSetupInstructions.tsx:169-172 — The new copy says Add Reactions is required, but effective channel diagnostics omit add_reactions from requiredPermissions; a denied reaction permission is still accepted as usable. Either enforce it in the diagnostics or keep the acknowledgment-only wording so setup guidance matches behavior.

_{Reviewed a20f3d1}

[roomote-roomote]

Fixed the outstanding review item: add_reactions is now required in Discord channel diagnostics (canUseChannel fails when it is denied).

Commit: a20f3d1