Cross-channel messaging, cron destinations, and admin agent gaps

Features

• Added cross-channel messaging support, enabling agents to send messages across different channels from a single interaction.
• Introduced cron destinations, allowing scheduled tasks to target specific delivery endpoints.
• Expanded Slack integration scoping to give finer control over which workspaces and channels agents can access.
• Closed six Admin Agent capability gaps (gaps 1, 3, 4, 6, 7, 8), covering a range of missing administrative operations.
• create_agent now attaches context files atomically in a single call, eliminating partial-state issues during agent creation.

Improvements

• Tightened tool authorization: cron tools are now available to any authenticated user, while anonymous access is scoped to the chat agent only.
• Clarified Profile session semantics in the UI and added confirmation warnings before destructive Profile or License actions.
• Overhauled the tool system internals — removed dual registries and established coordinator tool defaults for a simpler, more consistent tool resolution path.

Fixes

• Fixed list_threads to return thread IDs consistent with the schema expected by get_thread.
• Fixed a coordinator bug where the voice stash was not durably persisted across interim run_script executions.