Add remote script loader with intelligent completions

Features:
- Remote script execution with version control (name@ref)
- Background daemon for fast completions (< 15ms)
- HTTP caching with ETag/Last-Modified support
- Context-aware completions with async support
- Comprehensive documentation and type definitions

Changes:
- Add loader.ts with daemon mode
- Add completions.d.ts type definitions
- Add COMPLETIONS.md guide for developers
- Add README.md with usage examples
- Update configure_ssh_key.ts with async completions
- Use JSR imports for remote execution compatibility

configure_ssh_key.ts

@@ -26,9 +26,117 @@
  * from available keys in ~/.ssh or ssh-agent.
  */
 
-import { parseArgs } from "@std/cli/parse-args";
-import { expandGlob } from "@std/fs/expand-glob";
-import { join } from "@std/path";
+// Export completion function for loader
+import type { CompletionContext } from "./completions.d.ts";
+
+export async function getCompletions(ctx: CompletionContext): Promise<string[]> {
+  const { current, args } = ctx;
+  
+  // Helper to find SSH keys in ~/.ssh/
+  const findSSHKeys = async (): Promise<string[]> => {
+    try {
+      const home = Deno.env.get("HOME") || Deno.env.get("USERPROFILE") || "";
+      if (!home) return [];
+      const sshDir = `${home}/.ssh`;
+      const keys: string[] = [];
+      
+      try {
+        for await (const entry of Deno.readDir(sshDir)) {
+          if (entry.isFile && !entry.name.endsWith(".pub") && 
+              (entry.name.startsWith("id_") || entry.name.includes("key"))) {
+            keys.push(`--key=~/.ssh/${entry.name}`);
+          }
+        }
+      } catch {
+        // Fallback to common names if can't read directory
+        return ["--key=~/.ssh/id_rsa", "--key=~/.ssh/id_ed25519", "--key=~/.ssh/id_ecdsa"];
+      }
+      
+      return keys.length > 0 ? keys : ["--key=~/.ssh/id_rsa", "--key=~/.ssh/id_ed25519"];
+    } catch {
+      return ["--key=~/.ssh/id_rsa", "--key=~/.ssh/id_ed25519"];
+    }
+  };
+  
+  // If completing a value after --key=
+  if (current.startsWith("--key=")) {
+    const prefix = "--key=";
+    const value = current.slice(prefix.length);
+    
+    // If value is empty or starts with ~, suggest keys
+    if (!value || value.startsWith("~")) {
+      return await findSSHKeys();
+    }
+    // Otherwise suggest path completion hint
+    return ["--key=<path-to-private-key>"];
+  }
+  
+  // If completing --alias= value
+  if (current.startsWith("--alias=")) {
+    // Suggest format based on first positional arg if present
+    const target = args.find(a => !a.startsWith("-"));
+    if (target && target.includes("@")) {
+      const [user, host] = target.split("@");
+      const hostPart = host.split(":")[0];
+      return [`--alias=${user}-${hostPart.replace(/\./g, "-")}`];
+    }
+    return ["--alias=<host-alias>"];
+  }
+  
+  // If completing --port= value
+  if (current.startsWith("--port=")) {
+    return ["--port=22", "--port=2222", "--port=2200"];
+  }
+  
+  // If no flags yet and no target, suggest target format
+  const hasTarget = args.some(a => !a.startsWith("-") && a.includes("@"));
+  if (!hasTarget && !current.startsWith("-")) {
+    return ["user@hostname", "user@hostname:port"];
+  }
+  
+  // Check if certain flags already provided to avoid duplicates
+  const hasGenerate = args.includes("--generate");
+  const hasKey = args.some(a => a.startsWith("--key"));
+  const hasAlias = args.some(a => a.startsWith("--alias"));
+  const hasPort = args.some(a => a.startsWith("--port"));
+  const hasForce = args.includes("--force");
+  const hasDryRun = args.includes("--dry-run");
+  
+  const options: string[] = [];
+  
+  // Only suggest --key if --generate not present
+  if (!hasGenerate && !hasKey) {
+    options.push("--key=");
+  }
+  
+  if (!hasGenerate && !hasKey) {
+    options.push("--generate");
+  }
+  
+  if (!hasAlias) {
+    options.push("--alias=");
+  }
+  
+  if (!hasPort) {
+    options.push("--port=");
+  }
+  
+  if (!hasForce) {
+    options.push("--force");
+  }
+  
+  if (!hasDryRun) {
+    options.push("--dry-run");
+  }
+  
+  options.push("--help");
+  
+  return options;
+}
+
+import { parseArgs } from "jsr:@std/cli@^1.0.0/parse-args";
+import { expandGlob } from "jsr:@std/fs@^1.0.0/expand-glob";
+import { join } from "jsr:@std/path@^1.0.0";
 
 interface ParsedTarget {
   user: string;