Refactor WTA helper runtime ownership (#504)

* Refactor WTA helper runtime ownership

Move the per-pane helper TUI runtime out of main.rs and into the helper module without changing behavior. Document the broader incremental architecture refactor and correct the crate description.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: b3f5f1bc-78dd-4424-9417-88029e6535ad

* Remove local refactor plan from PR

Keep the architecture roadmap as an untracked local planning document rather than a repository artifact.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: b3f5f1bc-78dd-4424-9417-88029e6535ad

* Remove redundant helper channel import

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: b3f5f1bc-78dd-4424-9417-88029e6535ad

* Rename helper TUI module to runtime

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: b3f5f1bc-78dd-4424-9417-88029e6535ad

---------

Copilot-Session: b3f5f1bc-78dd-4424-9417-88029e6535ad

Author: vanzue

tools/wta/Cargo.toml

@@ -2,7 +2,7 @@
 name = "wta"
 version = "0.1.0"
 edition = "2021"
-description = "Windows Terminal Agent — ACP TUI client / MCP tool server"
+description = "Windows Terminal ACP agent bridge and control CLI"
 build = "build.rs"
 
 [[bin]]

tools/wta/src/helper/mod.rs

@@ -8,18 +8,18 @@
 // is passed in and speaks ACP JSON-RPC over it. From the helper's
 // perspective, master IS the agent.
 //
-// All App / event-loop machinery is reused from `run_default_tui_over_pipe`;
-// the only delta is the ACP transport, which is selected via
-// `--connect-master` and threaded down through `run_acp_app`, which drives
-// `run_acp_client_over_pipe` against the wta-master pipe.
+// The helper implementation lives in `helper/runtime.rs`: WT connection,
+// terminal lifecycle, channel wiring, and the event loop.
 
 use anyhow::Result;
 
 use crate::Cli;
 
+mod runtime;
+
 /// Helper-mode entry point. Routes the ACP traffic through a named pipe
 /// to the wta-master singleton instead of spawning a private agent CLI
 /// subprocess.
 pub async fn run_helper_mode(cli: Cli, pipe_name: String) -> Result<()> {
-    crate::run_default_tui_over_pipe(cli, pipe_name).await
+    runtime::run_default_tui_over_pipe(cli, pipe_name).await
 }