Update agent prompt, improve TUI patch UI, remove obsolete tool tests

- Replace and expand agent coder prompt for clarity and safety
- Add patch tool and TUI dialog support for patch diffs
- Sort sidebar modified files by name
- Remove Bash/Edit/Sourcegraph/Write tool tests

🤖 Generated with opencode
Co-Authored-By: opencode <noreply@opencode.ai>

internal/llm/agent/tools.go

@@ -31,6 +31,8 @@ func CoderAgentTools(
 			tools.NewGlobTool(),
 			tools.NewGrepTool(),
 			tools.NewLsTool(),
+			// TODO: see if we want to use this tool
+			// tools.NewPatchTool(lspClients, permissions, history),
 			tools.NewSourcegraphTool(),
 			tools.NewViewTool(lspClients),
 			tools.NewWriteTool(lspClients, permissions, history),