feat: add configurable CLI command and UI improvements

Add support for alternative CLI commands via CLI_COMMAND environment
variable, allowing users to use CLIs other than 'claude' (e.g., 'glm').
This change affects all server services and the main CLI launcher.

Key changes:

- Configurable CLI command via CLI_COMMAND env var (defaults to 'claude')
- Configurable Playwright headless mode via PLAYWRIGHT_HEADLESS env var
- Pin claude-agent-sdk version to <0.2.0 for stability
- Use tail -500 for progress notes to avoid context overflow
- Add project delete functionality with confirmation dialog
- Replace single-line input with resizable textarea in spec chat
- Add coder agent configuration for code implementation tasks
- Ignore issues/ directory in git

Files modified:
- client.py: CLI command and Playwright headless configuration
- server/main.py, server/services/*: CLI command configuration
- start.py: CLI command configuration and error messages
- .env.example: Document new environment variables
- .gitignore: Ignore issues/ directory
- requirements.txt: Pin SDK version
- .claude/templates/*: Use tail -500 for progress notes
- ui/src/components/ProjectSelector.tsx: Add delete button
- ui/src/components/SpecCreationChat.tsx: Auto-resizing textarea
- ui/src/components/ConfirmDialog.tsx: New reusable dialog
- .claude/agents/coder.md: New coder agent configuration

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

server/services/spec_chat_session.py

@@ -8,6 +8,7 @@ Uses the create-spec.md skill to guide users through app spec creation.
 
 import json
 import logging
+import os
 import shutil
 import threading
 from datetime import datetime
@@ -15,9 +16,23 @@ from pathlib import Path
 from typing import AsyncGenerator, Optional
 
 from claude_agent_sdk import ClaudeAgentOptions, ClaudeSDKClient
+from dotenv import load_dotenv
 
 from ..schemas import ImageAttachment
 
+# Load environment variables from .env file if present
+load_dotenv()
+
+
+def get_cli_command() -> str:
+    """
+    Get the CLI command to use for the agent.
+
+    Reads from CLI_COMMAND environment variable, defaults to 'claude'.
+    This allows users to use alternative CLIs like 'glm'.
+    """
+    return os.getenv("CLI_COMMAND", "claude")
+
 logger = logging.getLogger(__name__)
 
 
@@ -142,7 +157,9 @@ class SpecChatSession:
         # Create Claude SDK client with limited tools for spec creation
         # Use Opus for best quality spec generation
         # Use system CLI to avoid bundled Bun runtime crash (exit code 3) on Windows
-        system_cli = shutil.which("claude")
+        # CLI command is configurable via CLI_COMMAND environment variable
+        cli_command = get_cli_command()
+        system_cli = shutil.which(cli_command)
         try:
             self.client = ClaudeSDKClient(
                 options=ClaudeAgentOptions(