chore: Make terminal_view own the TerminalSlashCommand (#31070)

This reduces 'touch crates/editor/src/editor.rs && cargo +nightly build'
from 8.9s to 8.5s. That same scenario used to take 8s less than a week
ago. :)
I'm measuring with nightly rustc, because it's compile times are better
than those of stable thanks to
https://github.com/rust-lang/rust/pull/138522

main (8.2s total):

![image](https://github.com/user-attachments/assets/767a2ac4-7bba-4147-bd16-9b09eed5b433)

[cargo-timing.html.zip](https://github.com/user-attachments/files/20364175/cargo-timing.html.zip)

#22be776 (7.5s total):

[cargo-timing-20250521T085303.892834Z.html.zip](https://github.com/user-attachments/files/20364391/cargo-timing-20250521T085303.892834Z.html.zip)

![image](https://github.com/user-attachments/assets/c4476df9-cb6e-4403-b0db-de00521f1fd0)


Release Notes:

- N/A

crates/assistant_slash_commands/Cargo.toml

@@ -35,7 +35,6 @@ rope.workspace = true
 serde.workspace = true
 serde_json.workspace = true
 smol.workspace = true
-terminal_view.workspace = true
 text.workspace = true
 toml.workspace = true
 ui.workspace = true

crates/assistant_slash_commands/src/assistant_slash_commands.rs

@@ -12,11 +12,6 @@ mod selection_command;
 mod streaming_example_command;
 mod symbols_command;
 mod tab_command;
-mod terminal_command;
-
-use gpui::App;
-use language::{CodeLabel, HighlightId};
-use ui::ActiveTheme as _;
 
 pub use crate::cargo_workspace_command::*;
 pub use crate::context_server_command::*;
@@ -32,16 +27,5 @@ pub use crate::selection_command::*;
 pub use crate::streaming_example_command::*;
 pub use crate::symbols_command::*;
 pub use crate::tab_command::*;
-pub use crate::terminal_command::*;
 
-pub fn create_label_for_command(command_name: &str, arguments: &[&str], cx: &App) -> CodeLabel {
-    let mut label = CodeLabel::default();
-    label.push_str(command_name, None);
-    label.push_str(" ", None);
-    label.push_str(
-        &arguments.join(" "),
-        cx.theme().syntax().highlight_id("comment").map(HighlightId),
-    );
-    label.filter_range = 0..command_name.len();
-    label
-}
+use assistant_slash_command::create_label_for_command;

crates/assistant_slash_commands/src/terminal_command.rs

@@ -1,129 +0,0 @@
-use std::sync::Arc;
-use std::sync::atomic::AtomicBool;
-
-use anyhow::Result;
-use assistant_slash_command::{
-    ArgumentCompletion, SlashCommand, SlashCommandOutput, SlashCommandOutputSection,
-    SlashCommandResult,
-};
-use gpui::{App, Entity, Task, WeakEntity};
-use language::{BufferSnapshot, CodeLabel, LspAdapterDelegate};
-use terminal_view::{TerminalView, terminal_panel::TerminalPanel};
-use ui::prelude::*;
-use workspace::{Workspace, dock::Panel};
-
-use super::create_label_for_command;
-
-pub struct TerminalSlashCommand;
-
-const LINE_COUNT_ARG: &str = "--line-count";
-
-const DEFAULT_CONTEXT_LINES: usize = 50;
-
-impl SlashCommand for TerminalSlashCommand {
-    fn name(&self) -> String {
-        "terminal".into()
-    }
-
-    fn label(&self, cx: &App) -> CodeLabel {
-        create_label_for_command("terminal", &[LINE_COUNT_ARG], cx)
-    }
-
-    fn description(&self) -> String {
-        "Insert terminal output".into()
-    }
-
-    fn icon(&self) -> IconName {
-        IconName::Terminal
-    }
-
-    fn menu_text(&self) -> String {
-        self.description()
-    }
-
-    fn requires_argument(&self) -> bool {
-        false
-    }
-
-    fn accepts_arguments(&self) -> bool {
-        true
-    }
-
-    fn complete_argument(
-        self: Arc<Self>,
-        _arguments: &[String],
-        _cancel: Arc<AtomicBool>,
-        _workspace: Option<WeakEntity<Workspace>>,
-        _window: &mut Window,
-        _cx: &mut App,
-    ) -> Task<Result<Vec<ArgumentCompletion>>> {
-        Task::ready(Ok(Vec::new()))
-    }
-
-    fn run(
-        self: Arc<Self>,
-        arguments: &[String],
-        _context_slash_command_output_sections: &[SlashCommandOutputSection<language::Anchor>],
-        _context_buffer: BufferSnapshot,
-        workspace: WeakEntity<Workspace>,
-        _delegate: Option<Arc<dyn LspAdapterDelegate>>,
-        _: &mut Window,
-        cx: &mut App,
-    ) -> Task<SlashCommandResult> {
-        let Some(workspace) = workspace.upgrade() else {
-            return Task::ready(Err(anyhow::anyhow!("workspace was dropped")));
-        };
-
-        let Some(active_terminal) = resolve_active_terminal(&workspace, cx) else {
-            return Task::ready(Err(anyhow::anyhow!("no active terminal")));
-        };
-
-        let line_count = arguments
-            .get(0)
-            .and_then(|s| s.parse::<usize>().ok())
-            .unwrap_or(DEFAULT_CONTEXT_LINES);
-
-        let lines = active_terminal
-            .read(cx)
-            .entity()
-            .read(cx)
-            .last_n_non_empty_lines(line_count);
-
-        let mut text = String::new();
-        text.push_str("Terminal output:\n");
-        text.push_str(&lines.join("\n"));
-        let range = 0..text.len();
-
-        Task::ready(Ok(SlashCommandOutput {
-            text,
-            sections: vec![SlashCommandOutputSection {
-                range,
-                icon: IconName::Terminal,
-                label: "Terminal".into(),
-                metadata: None,
-            }],
-            run_commands_in_text: false,
-        }
-        .to_event_stream()))
-    }
-}
-
-fn resolve_active_terminal(
-    workspace: &Entity<Workspace>,
-    cx: &mut App,
-) -> Option<Entity<TerminalView>> {
-    if let Some(terminal_view) = workspace
-        .read(cx)
-        .active_item(cx)
-        .and_then(|item| item.act_as::<TerminalView>(cx))
-    {
-        return Some(terminal_view);
-    }
-
-    let terminal_panel = workspace.read(cx).panel::<TerminalPanel>(cx)?;
-    terminal_panel.read(cx).pane().and_then(|pane| {
-        pane.read(cx)
-            .active_item()
-            .and_then(|t| t.downcast::<TerminalView>())
-    })
-}