🔎 Global search for Talk messages

[Antreesy]

Tech proposal:

• embed in Search of app navigation (LeftSidebar)
• use the same UnifiedSearch endpoint as in RightSidebar > search (but not in current convo)
• opt-in and disabled by default
• controlled with filter chips

See linked PR for additional discussion and progress

[nickvergessen]

opt-in and disabled by default

We could "on click into the search field" show two chips [ Conversations ] [ Messages ] primary when selected, conversations being the default. Otherwise this is not easily discoverable and opt-in/out would mean you never see the other search results.