reactor(cli): move memoh cli to tui

1. Split the oversized `cmd/agent` entrypoint into a multi-file package and update dev/build scripts to use the package path instead of compiling `main.go` directly.
2. Add a new `memoh` terminal UI for local bot chat, with Bubble Tea

.air.toml

@@ -2,7 +2,7 @@ root = "."
 tmp_dir = "tmp"
 
 [build]
-cmd = "go build -o ./tmp/memoh-server ./cmd/agent/main.go && sh devenv/bridge-build.sh"
+cmd = "go build -o ./tmp/memoh-server ./cmd/agent && sh devenv/bridge-build.sh"
 bin = "./tmp/memoh-server"
 args_bin = ["serve"]
 include_ext = ["go", "toml"]