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/info.rs

@@ -0,0 +1,65 @@
+use crate::client::KeepClient;
+use crate::modes::common::{OutputFormat, format_size, settings_output_format};
+use clap::Command;
+use log::debug;
+
+pub fn mode(
+    client: &KeepClient,
+    _cmd: &mut Command,
+    settings: &crate::config::Settings,
+    ids: &[i64],
+    tags: &[String],
+) -> Result<(), anyhow::Error> {
+    debug!("CLIENT_INFO: Getting item info via remote server");
+
+    let output_format = settings_output_format(settings);
+
+    // If tags provided, find matching item first
+    let item_ids: Vec<i64> = if !tags.is_empty() {
+        let items = client.list_items(tags, "newest", 0, 1)?;
+        if items.is_empty() {
+            return Err(anyhow::anyhow!("No items found matching tags: {:?}", tags));
+        }
+        items.into_iter().map(|i| i.id).collect()
+    } else {
+        ids.to_vec()
+    };
+
+    for &id in &item_ids {
+        let item = client.get_item_info(id)?;
+
+        match output_format {
+            OutputFormat::Json => {
+                println!("{}", serde_json::to_string_pretty(&item)?);
+            }
+            OutputFormat::Yaml => {
+                println!("{}", serde_yaml::to_string(&item)?);
+            }
+            OutputFormat::Table => {
+                use comfy_table::{Table, presets::UTF8_FULL};
+
+                let mut table = Table::new();
+                table.load_preset(UTF8_FULL);
+
+                let size_str = item
+                    .size
+                    .map(|s| format_size(s as u64, settings.human_readable))
+                    .unwrap_or_else(|| "N/A".to_string());
+
+                table.add_row(vec!["ID".to_string(), item.id.to_string()]);
+                table.add_row(vec!["Time".to_string(), item.ts.clone()]);
+                table.add_row(vec!["Size".to_string(), size_str]);
+                table.add_row(vec!["Compression".to_string(), item.compression.clone()]);
+                table.add_row(vec!["Tags".to_string(), item.tags.join(", ")]);
+
+                for (key, value) in &item.metadata {
+                    table.add_row(vec![format!("Meta: {}", key), value.clone()]);
+                }
+
+                println!("{table}");
+            }
+        }
+    }
+
+    Ok(())
+}