[Docs] Explain Fast mode and cost detail behavior

apps/docs/cost-analytics.mdx

@@ -42,3 +42,7 @@ analytics is optional product telemetry sent to the Roomote team.
 If a provider does not report pricing or usage for a request, that request
 cannot contribute a cost to the view. Use provider and model filters to narrow
 an investigation when totals do not match an external provider invoice.
+
+The detail view consolidates recorded usage into one row per task. If a task
+used multiple users, environments, providers, or models, that column shows
+**Multiple** and the row includes the task's combined cost.

apps/docs/providers/communications/discord.mdx

@@ -130,6 +130,10 @@ under **Settings > Automations**, the same way you would pick a Slack channel.
   (lookups outside the originating task thread require a linked Discord account)
 - use `/help` to see the available commands
 
+Fast answers can use the conversation, the deployment's Brain, and enabled
+deployment integrations to answer directly. Requests that need repository or
+workspace execution are delegated to a normal Roomote task.
+
 Roomote does not quote every message it answers. In a task thread, the
 conversation itself supplies the context. When you start a task by tagging
 Roomote in an existing thread, Roomote reads earlier messages in that thread

apps/docs/providers/communications/slack.mdx

@@ -166,6 +166,10 @@ question or delegate work into a task. For example: `@Roomote /fast summarize
 this thread` or `@Roomote /fast fix the failing CI job`. The earlier
 `!fast <request>` form remains supported for compatibility.
 
+Fast answers can use the conversation, the deployment's Brain, and enabled
+deployment integrations to answer directly. Requests that need repository or
+workspace execution are delegated to a normal Roomote task.
+
 When your deployment exposes **Default messages to fast mode**, enable it under
 **Settings > Personal** to send ordinary Slack and Discord messages through the
 fast orchestrator without an explicit command.