Start on adding support for editing via the assistant panel (#14795)

Note that this shouldn't have any visible user-facing behavior yet. The
feature is incomplete but we wanna merge early to avoid a long-running
branch.

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/assistant/Cargo.toml

@@ -23,6 +23,7 @@ test-support = [
 [dependencies]
 anthropic = { workspace = true, features = ["schemars"] }
 anyhow.workspace = true
+assets.workspace = true
 assistant_slash_command.workspace = true
 async-watch.workspace = true
 breadcrumbs.workspace = true
@@ -63,7 +64,6 @@ serde_json.workspace = true
 settings.workspace = true
 similar.workspace = true
 smol.workspace = true
-strsim = "0.11"
 strum.workspace = true
 telemetry_events.workspace = true
 terminal.workspace = true
@@ -76,6 +76,7 @@ util.workspace = true
 uuid.workspace = true
 workspace.workspace = true
 picker.workspace = true
+roxmltree = "0.20.0"
 
 [dev-dependencies]
 ctor.workspace = true