feat: add /commands reload to refresh custom TOML commands (#19078)

docs/cli/commands.md

@@ -71,6 +71,17 @@ Slash commands provide meta-level control over the CLI itself.
   the visual display is cleared.
 - **Keyboard shortcut:** Press **Ctrl+L** at any time to perform a clear action.
 
+### `/commands`
+
+- **Description:** Manage custom slash commands loaded from `.toml` files.
+- **Sub-commands:**
+  - **`reload`**:
+    - **Description:** Reload custom command definitions from all sources
+      (user-level `~/.gemini/commands/`, project-level
+      `<project>/.gemini/commands/`, MCP prompts, and extensions). Use this to
+      pick up new or modified `.toml` files without restarting the CLI.
+    - **Usage:** `/commands reload`
+
 ### `/compress`
 
 - **Description:** Replace the entire chat context with a summary. This saves on