Add outline-cli: minimal CLI for search and document retrieval

Adds a command-line client in cli/ as its own Cargo workspace, depending
on the outline library via a path dependency. Covers exactly the requested
scope: login (stores the API key in the system keyring via the Secret
Service D-Bus protocol, verified against auth.info() before storing),
search (full-text), and get (fetch a document, render its markdown to a
self-contained HTML page, open it in the default browser).

Verified end-to-end against a real Outline instance and the local
gnome-keyring: login stores and search/get retrieve the token purely from
the keyring and saved config, with no environment variables set.

cli/src/cli.rs

@@ -0,0 +1,52 @@
+use clap::{Args, Parser, Subcommand};
+
+#[derive(Debug, Parser)]
+#[command(
+    name = "outline",
+    version,
+    about = "Search and read Outline documents from the terminal"
+)]
+pub struct Cli {
+    /// Outline instance to talk to (default: <https://app.getoutline.com>)
+    #[arg(long, global = true, value_name = "URL", env = "OUTLINE_URL")]
+    pub base_url: Option<String>,
+
+    /// API key. Prefer `outline login`: arguments are visible in the process list.
+    #[arg(
+        long,
+        global = true,
+        value_name = "KEY",
+        env = "OUTLINE_API_KEY",
+        hide_env_values = true
+    )]
+    pub api_key: Option<String>,
+
+    #[command(subcommand)]
+    pub command: Command,
+}
+
+#[derive(Debug, Subcommand)]
+pub enum Command {
+    /// Store an API key for the configured Outline instance in the system keyring
+    Login,
+    /// Full-text search documents
+    Search(SearchArgs),
+    /// Fetch a document, render it to HTML and open it in the browser
+    Get(GetArgs),
+}
+
+#[derive(Debug, Args)]
+pub struct SearchArgs {
+    /// The search query
+    pub query: String,
+
+    /// Maximum number of results to show
+    #[arg(short = 'n', long, default_value_t = 10)]
+    pub limit: u32,
+}
+
+#[derive(Debug, Args)]
+pub struct GetArgs {
+    /// Document id, urlId, or a full Outline document URL
+    pub reference: String,
+}