feat(daemon): route commands and the TUI through a running daemon

Session::open attaches to a daemon when one is reachable and logs in
otherwise, so every existing command works unchanged against either. A local
socket is found automatically, which is what makes an agent's invocation need
no flags at all; --no-daemon opts out.

Commands now read identity, shares, server, and download directory from the
session rather than from this run's config: routed to a daemon those differ,
and the session is the one actually on the network. Without that, whoami
named the wrong server and shares reindex would have imposed the client
machine's folders on the daemon.

soulseek-rs/src/commands/transfer.rs

@@ -240,7 +240,7 @@ pub fn download(ctx: &Ctx, args: &DownloadArgs) -> CliResult {
         return Err(CliError::no_results("no files to download"));
     }
 
-    ensure_download_dir(&ctx.download_dir)?;
+    ensure_download_dir(ctx)?;
     let session = Session::open(ctx)?;
     let requests = resolve_sizes(ctx, session.client.as_ref(), requests)?;
     download_all(
@@ -252,7 +252,7 @@ pub fn download(ctx: &Ctx, args: &DownloadArgs) -> CliResult {
 }
 
 pub fn get(ctx: &Ctx, args: &GetArgs) -> CliResult {
-    ensure_download_dir(&ctx.download_dir)?;
+    ensure_download_dir(ctx)?;
     let session = Session::open(ctx)?;
     let results =
         collect(ctx, &session.client, &args.query, args.pick == Pick::First)?;
@@ -421,8 +421,17 @@ fn resolve_sizes(
     Ok(resolved)
 }
 
-fn ensure_download_dir(download_dir: &str) -> CliResult {
-    let path = expand_tilde(download_dir);
+/// Make sure the bytes have somewhere to land.
+///
+/// A daemon writes to its own filesystem and has already done this; creating
+/// the same path here would leave a stray directory on the client machine and,
+/// for a daemon on another host, could fail outright over a path that is none
+/// of this machine's business.
+fn ensure_download_dir(ctx: &Ctx) -> CliResult {
+    if ctx.daemon.is_some() {
+        return Ok(());
+    }
+    let path = expand_tilde(&ctx.download_dir);
     std::fs::create_dir_all(&path).map_err(|e| {
         CliError::usage(format!(
             "cannot use download directory {}: {e}",