feat(cli): add interactive REPL mode with agent loop

Add proper interactive mode when no prompt is provided:

**Interactive REPL Features**:
- Starts when running `cargo run` with no arguments
- Shows welcome message with model name
- Prompts with `> ` for user input
- Each input runs through the full agent loop with tools
- Continues until Ctrl+C or EOF
- Displays tool calls and results in real-time

**Changes**:
- Detect empty prompt and enter interactive loop
- Use stdin.lines() for reading user input
- Call agent_core::run_agent_loop for each message
- Handle errors gracefully and continue
- Clean up unused imports

**Usage**:
```bash
# Interactive mode
cargo run

# Single prompt mode
cargo run -- --print "Find all Cargo.toml files"

# Tool subcommands
cargo run -- glob "**/*.rs"
```

Example session:
```
🤖 Owlen Interactive Mode
Model: qwen3:8b

> Find all markdown files
🔧 Tool call: glob with args: {"pattern":"**/*.md"}
✅ Tool result: ./README.md ./CLAUDE.md ./AGENTS.md
...

> exit
```

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

crates/app/cli/src/main.rs

@@ -1,12 +1,11 @@
 use clap::{Parser, ValueEnum};
 use color_eyre::eyre::{Result, eyre};
 use config_agent::load_settings;
-use futures_util::TryStreamExt;
 use hooks::{HookEvent, HookManager, HookResult};
-use llm_ollama::{OllamaClient, OllamaOptions, types::ChatMessage};
+use llm_ollama::{OllamaClient, OllamaOptions};
 use permissions::{PermissionDecision, Tool};
 use serde::Serialize;
-use std::io::{self, Write};
+use std::io::Write;
 use std::time::{SystemTime, UNIX_EPOCH};
 
 #[derive(Debug, Clone, Copy, ValueEnum)]
@@ -435,12 +434,6 @@ async fn main() -> Result<()> {
         }
     }
 
-    let prompt = if args.prompt.is_empty() {
-        "Say hello".to_string()
-    } else {
-        args.prompt.join(" ")
-    };
-
     let model = args.model.unwrap_or(settings.model);
     let api_key = args.api_key.or(settings.api_key);
 
@@ -461,6 +454,45 @@ async fn main() -> Result<()> {
         stream: true,
     };
 
+    // Check if interactive mode (no prompt provided)
+    if args.prompt.is_empty() {
+        println!("🤖 Owlen Interactive Mode");
+        println!("Model: {}", opts.model);
+        println!("Type your message and press Enter. Press Ctrl+C to exit.\n");
+
+        use std::io::{stdin, BufRead};
+        let stdin = stdin();
+        let mut lines = stdin.lock().lines();
+
+        loop {
+            print!("\n> ");
+            std::io::stdout().flush().ok();
+
+            if let Some(Ok(line)) = lines.next() {
+                let prompt = line.trim();
+                if prompt.is_empty() {
+                    continue;
+                }
+
+                // Run agent loop for this prompt
+                match agent_core::run_agent_loop(&client, prompt, &opts, &perms).await {
+                    Ok(response) => {
+                        println!("\n{}", response);
+                    }
+                    Err(e) => {
+                        eprintln!("\n❌ Error: {}", e);
+                    }
+                }
+            } else {
+                break;
+            }
+        }
+
+        return Ok(());
+    }
+
+    // Non-interactive mode - process single prompt
+    let prompt = args.prompt.join(" ");
     let start_time = SystemTime::now();
 
     // Handle different output formats