Factor tool definitions out of assistant (#21189)

This PR factors the tool definitions out of the `assistant` crate so
that they can be shared between `assistant` and `assistant2`.

`ToolWorkingSet` now lives in `assistant_tool`. The tool definitions
themselves live in `assistant_tools`, with the exception of the
`ContextServerTool`, which has been moved to the `context_server` crate.

As part of this refactoring I needed to extract the
`ContextServerSettings` to a separate `context_server_settings` crate so
that the `extension_host`—which is referenced by the `remote_server`—can
name the `ContextServerSettings` type without pulling in some undesired
dependencies.

Release Notes:

- N/A

crates/assistant/src/assistant.rs

@@ -14,16 +14,12 @@ pub mod slash_command_settings;
 mod slash_command_working_set;
 mod streaming_diff;
 mod terminal_inline_assistant;
-mod tool_working_set;
-mod tools;
 
 use crate::slash_command::project_command::ProjectSlashCommandFeatureFlag;
 pub use crate::slash_command_working_set::{SlashCommandId, SlashCommandWorkingSet};
-pub use crate::tool_working_set::{ToolId, ToolWorkingSet};
 pub use assistant_panel::{AssistantPanel, AssistantPanelEvent};
 use assistant_settings::AssistantSettings;
 use assistant_slash_command::SlashCommandRegistry;
-use assistant_tool::ToolRegistry;
 use client::{proto, Client};
 use command_palette_hooks::CommandPaletteFilter;
 pub use context::*;
@@ -246,7 +242,7 @@ pub fn init(
     assistant_slash_command::init(cx);
     assistant_tool::init(cx);
     assistant_panel::init(cx);
-    context_servers::init(cx);
+    context_server::init(cx);
 
     let prompt_builder = prompts::PromptBuilder::new(Some(PromptLoadingParams {
         fs: fs.clone(),
@@ -259,7 +255,6 @@ pub fn init(
     .map(Arc::new)
     .unwrap_or_else(|| Arc::new(prompts::PromptBuilder::new(None).unwrap()));
     register_slash_commands(Some(prompt_builder.clone()), cx);
-    register_tools(cx);
     inline_assistant::init(
         fs.clone(),
         prompt_builder.clone(),
@@ -423,11 +418,6 @@ fn update_slash_commands_from_settings(cx: &mut AppContext) {
     }
 }
 
-fn register_tools(cx: &mut AppContext) {
-    let tool_registry = ToolRegistry::global(cx);
-    tool_registry.register_tool(tools::now_tool::NowTool);
-}
-
 pub fn humanize_token_count(count: usize) -> String {
     match count {
         0..=999 => count.to_string(),