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>

client.py

@@ -13,9 +13,45 @@ from pathlib import Path
 
 from claude_agent_sdk import ClaudeAgentOptions, ClaudeSDKClient
 from claude_agent_sdk.types import HookMatcher
+from dotenv import load_dotenv
 
 from security import bash_security_hook
 
+# Load environment variables from .env file if present
+load_dotenv()
+
+# Default CLI command - can be overridden via CLI_COMMAND environment variable
+# Common values: "claude" (default), "glm"
+DEFAULT_CLI_COMMAND = "claude"
+
+# Default Playwright headless mode - can be overridden via PLAYWRIGHT_HEADLESS env var
+# When True, browser runs invisibly in background
+# When False, browser window is visible (default - useful for monitoring agent progress)
+DEFAULT_PLAYWRIGHT_HEADLESS = False
+
+
+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", DEFAULT_CLI_COMMAND)
+
+
+def get_playwright_headless() -> bool:
+    """
+    Get the Playwright headless mode setting.
+
+    Reads from PLAYWRIGHT_HEADLESS environment variable, defaults to False.
+    Returns True for headless mode (invisible browser), False for visible browser.
+    """
+    value = os.getenv("PLAYWRIGHT_HEADLESS", "false").lower()
+    # Accept various truthy/falsy values
+    return value in ("true", "1", "yes", "on")
+
+
 # Feature MCP tools for feature/test management
 FEATURE_MCP_TOOLS = [
     "mcp__features__feature_get_stats",
@@ -151,12 +187,14 @@ def create_client(project_dir: Path, model: str, yolo_mode: bool = False):
     print("   - Project settings enabled (skills, commands, CLAUDE.md)")
     print()
 
-    # Use system Claude CLI instead of bundled one (avoids Bun runtime crash on Windows)
-    system_cli = shutil.which("claude")
+    # Use system CLI instead of bundled one (avoids Bun runtime crash on Windows)
+    # CLI command is configurable via CLI_COMMAND environment variable
+    cli_command = get_cli_command()
+    system_cli = shutil.which(cli_command)
     if system_cli:
         print(f"   - Using system CLI: {system_cli}")
     else:
-        print("   - Warning: System Claude CLI not found, using bundled CLI")
+        print(f"   - Warning: System CLI '{cli_command}' not found, using bundled CLI")
 
     # Build MCP servers config - features is always included, playwright only in standard mode
     mcp_servers = {
@@ -174,9 +212,13 @@ def create_client(project_dir: Path, model: str, yolo_mode: bool = False):
     }
     if not yolo_mode:
         # Include Playwright MCP server for browser automation (standard mode only)
+        # Headless mode is configurable via PLAYWRIGHT_HEADLESS environment variable
+        playwright_args = ["@playwright/mcp@latest", "--viewport-size", "1280x720"]
+        if get_playwright_headless():
+            playwright_args.append("--headless")
         mcp_servers["playwright"] = {
             "command": "npx",
-            "args": ["@playwright/mcp@latest", "--viewport-size", "1280x720"],
+            "args": playwright_args,
         }
 
     return ClaudeSDKClient(