feat(commands): add input_clear

sometimes nice to have

Author: NickvanDyke

README.md

@@ -147,6 +147,7 @@ Send a [command](https://opencode.ai/docs/keybinds):
 | `messages_copy`           | Copy the last message in the session                     |
 | `messages_undo`           | Undo the last message in the session                     |
 | `messages_redo`           | Redo the last message in the session                     |
+| `input_clear`             | Clear the TUI input                                      |
 | `agent_cycle`             | Cycle the selected agent                                 |
 
 > Supports *all* commands — these are just the most useful ones.

lua/opencode.lua

@@ -97,6 +97,7 @@ end
 ---| 'messages_copy'
 ---| 'messages_undo'
 ---| 'messages_redo'
+---| 'input_clear'
 ---| 'agent_cycle'
 
 ---Send a [command](https://opencode.ai/docs/keybinds) to `opencode`.
@@ -121,6 +122,7 @@ function M.command(command, callback)
           { name = "Copy last message", command = "messages_copy" },
           { name = "Undo last message", command = "messages_undo" },
           { name = "Redo last message", command = "messages_redo" },
+          { name = "Clear input", command = "input_clear" },
           { name = "Cycle agent", command = "agent_cycle" },
         }, {
           prompt = "Command opencode: ",