feat: add client mode with streaming support

Add client mode enabling the keep CLI to connect to a remote keep
server over HTTP. Local plugins (compression, meta, filters) run on
the client; the server stores/retrieves binary blobs.

Architecture:
- Client save uses 3-thread streaming pipeline: reader thread (stdin
  → tee/stdout → hash → compress), OS pipe, streamer thread (pipe →
  chunked HTTP POST). Memory usage is O(PIPESIZE) regardless of data
  size.
- Server accepts compress=false, meta=false, decompress=false query
  params for granular control of server-side processing.
- Streaming body handling on server via async channel → sync reader
  bridge (ChannelReader).

Key additions:
- src/client.rs: KeepClient with post_stream() for chunked upload
- src/modes/client/: save, get, list, info, delete, diff, status
- --client-url / KEEP_CLIENT_URL configuration
- --client-password / KEEP_CLIENT_PASSWORD for auth
- os_pipe dependency for zero-copy pipe streaming

Co-Authored-By: andrew/openrouter/hunter-alpha <noreply@opencode.ai>

src/modes/client/status.rs

@@ -0,0 +1,33 @@
+use crate::client::KeepClient;
+use crate::modes::common::OutputFormat;
+use crate::modes::common::settings_output_format;
+use clap::Command;
+use log::debug;
+
+pub fn mode(
+    client: &KeepClient,
+    _cmd: &mut Command,
+    settings: &crate::config::Settings,
+) -> Result<(), anyhow::Error> {
+    debug!("CLIENT_STATUS: Getting status from remote server");
+
+    let status = client.get_status()?;
+
+    let output_format = settings_output_format(settings);
+
+    match output_format {
+        OutputFormat::Json => {
+            println!("{}", serde_json::to_string_pretty(&status)?);
+        }
+        OutputFormat::Yaml => {
+            println!("{}", serde_yaml::to_string(&status)?);
+        }
+        OutputFormat::Table => {
+            println!("Remote Server Status");
+            println!("====================");
+            println!("{}", serde_json::to_string_pretty(&status)?);
+        }
+    }
+
+    Ok(())
+}