M1: composition root and harness run -p debug command

Adds the harness-app composition root wiring config, providers, tools, and the engine loop together, plus the harness run -p "<prompt>" debug command in harness-tui::main for driving a one-shot prompt end-to-end from the CLI.

Cargo.lock

@@ -509,11 +509,16 @@ dependencies = [
 name = "harness-app"
 version = "0.1.0"
 dependencies = [
+ "dirs",
  "harness-core",
  "harness-lsp",
  "harness-mcp",
  "harness-providers",
  "harness-tools",
+ "tempfile",
+ "thiserror 2.0.18",
+ "tokio",
+ "tokio-util",
 ]
 
 [[package]]
@@ -598,6 +603,8 @@ name = "harness-tui"
 version = "0.1.0"
 dependencies = [
  "harness-app",
+ "harness-core",
+ "tokio",
 ]
 
 [[package]]