feat(cli): Add 'list' subcommand to '/commands' (#22324)

Co-authored-by: Coco Sheng <cocosheng@google.com>
Co-authored-by: Spencer <spencertang@google.com>

docs/cli/cli-reference.md

@@ -33,6 +33,7 @@ These commands are available within the interactive REPL.
 | -------------------- | ----------------------------------------------- |
 | `/skills reload`     | Reload discovered skills from disk              |
 | `/agents reload`     | Reload the agent registry                       |
+| `/commands list`     | List available custom slash commands            |
 | `/commands reload`   | Reload custom slash commands                    |
 | `/memory reload`     | Reload context files (for example, `GEMINI.md`) |
 | `/mcp reload`        | Restart and reload MCP servers                  |

docs/cli/custom-commands.md

@@ -34,6 +34,7 @@ separator (`/` or `\`) being converted to a colon (`:`).
 > [!TIP]
 > After creating or modifying `.toml` command files, run
 > `/commands reload` to pick up your changes without restarting the CLI.
+> To see all available command files, run `/commands list`.
 
 ## TOML file format (v1)
 

docs/reference/commands.md

@@ -111,6 +111,11 @@ Slash commands provide meta-level control over the CLI itself.
 
 - **Description:** Manage custom slash commands loaded from `.toml` files.
 - **Sub-commands:**
+  - **`list`**:
+    - **Description:** List available custom command `.toml` files from all
+      sources (user-level `~/.gemini/commands/`, project-level
+      `<project>/.gemini/commands/`, and active extensions).
+    - **Usage:** `/commands list`
   - **`reload`**:
     - **Description:** Reload custom command definitions from all sources
       (user-level `~/.gemini/commands/`, project-level