fix(agents): Complete project skills and custom commands in the agent composer

The `/` completion of the New Task page only listed the commands the agent
offered in its last session, cached once for all projects, and matched them
by substring. Before a project's first session, or after a session in another
project, its skills were missing, and `/trig` never matched `/triage`.

- Remember the commands an agent offered per project root (settings stay shared).
- New `agent_commands` command: the agent's last list for the project (or the
  task's own list in a session) merged with, for Claude Code, the skills
  (`.claude/skills/*/SKILL.md`) and custom commands (`.claude/commands/**/*.md`,
  nested as `dir:name`) found from the working directory upward and in
  `~/.claude`. The agent's entries win on a name; skills with
  `user-invocable: false` are left out. Discovery runs off the command thread.
- Sessions discover from the task's own directory (worktree or checkout).
- Command matching ranks prefix, plugin-name prefix, substring, then letters in order.

Claude-Session: https://claude.ai/code/session_01VUYsdXA2nkF5v6zsC93dpn

src-tauri/src/commands/agent.rs

@@ -1,6 +1,6 @@
 use crate::state::AppState;
 use ide_agent::{
-    AgentChange, AgentEntry, AgentEvent, AgentPrompt, AgentProvider, AgentQueued, AgentTask, NewAgentTask,
+    AgentChange, AgentCommand, AgentEntry, AgentEvent, AgentPrompt, AgentProvider, AgentQueued, AgentTask, NewAgentTask,
 };
 use ide_core::{IdeResult, IpcPath};
 use std::sync::Arc;
@@ -27,6 +27,20 @@ pub fn agent_providers(window: Window, state: State<'_, AppState>) -> IdeResult<
     Ok(state.project(window.label())?.agents.providers())
 }
 
+/// Slash commands to complete for `provider` in `task`'s directory, or in the project
+/// before a task exists (skills and custom commands on disk included).
+#[tauri::command]
+#[specta::specta]
+pub async fn agent_commands(
+    window: Window,
+    state: State<'_, AppState>,
+    provider: String,
+    task: Option<String>,
+) -> IdeResult<Vec<AgentCommand>> {
+    let project = state.project(window.label())?;
+    project.agents.commands(&provider, task.as_deref()).await
+}
+
 #[tauri::command]
 #[specta::specta]
 pub fn agent_entries(window: Window, state: State<'_, AppState>, task: String) -> IdeResult<Vec<AgentEntry>> {

src-tauri/src/commands/mod.rs

@@ -62,6 +62,7 @@ pub fn builder() -> tauri_specta::Builder<tauri::Wry> {
         app::log_frontend,
         agent::agent_subscribe,
         agent::agent_providers,
+        agent::agent_commands,
         agent::agent_entries,
         agent::agent_create,
         agent::agent_prompt,

src-tauri/src/state.rs

@@ -417,6 +417,7 @@ impl AppState {
                     .join(&project_key),
                 models_file: self.data_dir.join("agents").join("models.json"),
                 custom_agents_dir: Some(self.config_dir.join("agents")),
+                home_dir: dirs::home_dir(),
             },
             tauri::async_runtime::handle().inner().clone(),
         ));