agent: Use inventory for AgentPreview (#30740)

This PR updates the `AgentPreview` to use `inventory` instead of
`linkme`.

Release Notes:

- N/A

crates/ui/Cargo.toml

@@ -19,7 +19,6 @@ documented.workspace = true
 gpui.workspace = true
 icons.workspace = true
 itertools.workspace = true
-linkme.workspace = true
 menu.workspace = true
 serde.workspace = true
 settings.workspace = true
@@ -37,7 +36,3 @@ windows.workspace = true
 [features]
 default = []
 stories = ["dep:story"]
-
-# cargo-machete doesn't understand that linkme is used in the component macro
-[package.metadata.cargo-machete]
-ignored = ["linkme"]