Unify intent selector, model selector, and agentic chat dropdown

[beyang]

omni-selector.mov

TODO

• Icons
• setAgent (setHandler) should also set model
• Remove intent status update except when using 'auto' handler
• Update intent button
• Update ToolboxManager
• Remove hardcoded "deep-cody" (all instances)
• Default agentID needs to be consistent with what's selected in UI (right now defaults to "deep-cody")
• When code search intent is detected with "agentic chat" selected, response is empty
• fix getTooltip
• "Agent" -> "Handler" renames
• Create chat/setAgent handler
• Fix tests

Later

• Port ToolCody over

Test plan

Test locally

[aramaraju]

🤔

[abeatrix]

Haven't tested the build locally but left some questions inline about the missing feature flags check for agentic chat (deep cody) - do we need to add them back?

[abeatrix]

Do we still need to check if they have the feature flags for agentic chat and terminal access before we add the handler?

[beyang]

Nope, agentic chat is now enabled by default and terminal access I think we should just turn on, given that it always asks for permission anyway.