feat: add multiline input support with Shift+Enter and bracketed paste

- Enable kitty keyboard protocol for Shift+Enter support in iTerm2, kitty,
  WezTerm, and alacritty
- Add Alt+Enter as fallback for terminals without kitty protocol
- Enable bracketed paste mode so pasted multiline content doesn't auto-submit
- Add documentation tests explaining manual testing requirements (PTY
  environments don't support these terminal features)

Addresses #24 - multiline input support in REPL

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: evansenter

src/main.rs

@@ -2,7 +2,10 @@ use anyhow::Result;
 use clap::Parser;
 use colored::Colorize;
 use genai_rs::Client;
-use reedline::{FileBackedHistory, Prompt, PromptHistorySearch, Reedline, Signal};
+use reedline::{
+    default_emacs_keybindings, EditCommand, Emacs, FileBackedHistory, KeyCode, KeyModifiers,
+    Prompt, PromptHistorySearch, Reedline, ReedlineEvent, Signal, kitty_protocol_available,
+};
 use serde::Deserialize;
 use std::borrow::Cow;
 use std::env;
@@ -663,8 +666,35 @@ fn spawn_reedline_thread(
             }
         };
 
-        // Create reedline editor
-        let mut line_editor = Reedline::create();
+        // Create reedline editor with custom keybindings
+        let mut keybindings = default_emacs_keybindings();
+        // Shift+Enter inserts a newline for multiline input
+        // Requires kitty keyboard protocol for Shift modifier detection
+        keybindings.add_binding(
+            KeyModifiers::SHIFT,
+            KeyCode::Enter,
+            ReedlineEvent::Edit(vec![EditCommand::InsertNewline]),
+        );
+        // Also bind Alt+Enter as fallback for terminals without kitty protocol
+        keybindings.add_binding(
+            KeyModifiers::ALT,
+            KeyCode::Enter,
+            ReedlineEvent::Edit(vec![EditCommand::InsertNewline]),
+        );
+        let edit_mode = Box::new(Emacs::new(keybindings));
+
+        // Enable kitty keyboard protocol for better modifier key detection
+        // (Shift+Enter, etc.) in supported terminals (iTerm2, kitty, WezTerm, alacritty)
+        let use_kitty = kitty_protocol_available();
+        if use_kitty {
+            tracing::debug!("Kitty keyboard protocol available, enabling enhanced key detection");
+        }
+
+        let mut line_editor = Reedline::create()
+            .with_edit_mode(edit_mode)
+            .use_kitty_keyboard_enhancement(use_kitty)
+            // Enable bracketed paste so multiline pastes don't auto-submit on each newline
+            .use_bracketed_paste(true);
         if let Some(h) = history {
             line_editor = line_editor.with_history(h);
         }

tests/terminal_tests.rs

@@ -764,3 +764,58 @@ fn test_ctrl_d_exits() {
     // Process should exit
     wait_for_exit(&mut session).expect("Process should have exited");
 }
+
+// ============================================================================
+// Multiline Input Tests
+// ============================================================================
+
+/// Multiline input via Shift+Enter or Alt+Enter.
+///
+/// **Manual testing required** - PTY environments don't support the kitty keyboard
+/// protocol needed for Shift+Enter, and Alt+Enter escape sequences are interpreted
+/// differently across terminal emulators.
+///
+/// To test manually:
+/// 1. Run `cargo run` or the release binary
+/// 2. Type some text
+/// 3. Press Shift+Enter (in iTerm2, kitty, WezTerm, alacritty) or Alt+Enter
+/// 4. Should insert a newline and show the multiline indicator ("  ")
+/// 5. Type more text and press Enter to submit the full multiline input
+#[test]
+#[ignore = "Manual testing only - PTY doesn't support kitty keyboard protocol"]
+fn test_multiline_input_manual() {
+    // This test exists as documentation for manual testing.
+    // Automated PTY testing of keyboard shortcuts with modifiers is unreliable
+    // because PTYs don't support the kitty keyboard protocol.
+    eprintln!("This test requires manual verification:");
+    eprintln!("1. Run clemini");
+    eprintln!("2. Type text, press Shift+Enter or Alt+Enter");
+    eprintln!("3. Verify newline is inserted with multiline indicator");
+}
+
+/// Bracketed paste for multiline content.
+///
+/// **Manual testing required** - PTY environments don't support bracketed paste mode.
+/// Bracketed paste is a terminal emulator feature where the terminal wraps pasted
+/// content with `ESC[200~` ... `ESC[201~` escape sequences. PTY testing libraries
+/// don't emulate this terminal feature.
+///
+/// To test manually:
+/// 1. Run `cargo run` or the release binary
+/// 2. Copy multiline text to clipboard
+/// 3. Paste into clemini (Cmd+V / Ctrl+Shift+V)
+/// 4. Content should appear in buffer with newlines preserved
+/// 5. Press Enter to submit the entire multiline input
+///
+/// Without bracketed paste, each newline would submit immediately.
+#[test]
+#[ignore = "Manual testing only - PTY doesn't support bracketed paste mode"]
+fn test_bracketed_paste_manual() {
+    // This test exists as documentation for manual testing.
+    // PTYs don't support bracketed paste mode - it's a terminal emulator feature.
+    eprintln!("This test requires manual verification:");
+    eprintln!("1. Run clemini");
+    eprintln!("2. Copy multiline text and paste it");
+    eprintln!("3. Verify all lines appear in the input buffer");
+    eprintln!("4. Press Enter to submit");
+}