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>

ui/src/components/ConfirmDialog.tsx

@@ -0,0 +1,103 @@
+/**
+ * ConfirmDialog Component
+ *
+ * A reusable confirmation dialog following the neobrutalism design system.
+ * Used to confirm destructive actions like deleting projects.
+ */
+
+import { AlertTriangle, X } from 'lucide-react'
+
+interface ConfirmDialogProps {
+  isOpen: boolean
+  title: string
+  message: string
+  confirmLabel?: string
+  cancelLabel?: string
+  variant?: 'danger' | 'warning'
+  isLoading?: boolean
+  onConfirm: () => void
+  onCancel: () => void
+}
+
+export function ConfirmDialog({
+  isOpen,
+  title,
+  message,
+  confirmLabel = 'Confirm',
+  cancelLabel = 'Cancel',
+  variant = 'danger',
+  isLoading = false,
+  onConfirm,
+  onCancel,
+}: ConfirmDialogProps) {
+  if (!isOpen) return null
+
+  const variantColors = {
+    danger: {
+      icon: 'var(--color-neo-danger)',
+      button: 'neo-btn-danger',
+    },
+    warning: {
+      icon: 'var(--color-neo-pending)',
+      button: 'neo-btn-warning',
+    },
+  }
+
+  const colors = variantColors[variant]
+
+  return (
+    <div className="neo-modal-backdrop" onClick={onCancel}>
+      <div
+        className="neo-modal w-full max-w-md"
+        onClick={(e) => e.stopPropagation()}
+      >
+        {/* Header */}
+        <div className="flex items-center justify-between p-4 border-b-3 border-[var(--color-neo-border)]">
+          <div className="flex items-center gap-3">
+            <div
+              className="p-2 border-2 border-[var(--color-neo-border)] shadow-[2px_2px_0px_rgba(0,0,0,1)]"
+              style={{ backgroundColor: colors.icon }}
+            >
+              <AlertTriangle size={20} className="text-white" />
+            </div>
+            <h2 className="font-display font-bold text-lg text-[#1a1a1a]">
+              {title}
+            </h2>
+          </div>
+          <button
+            onClick={onCancel}
+            className="neo-btn neo-btn-ghost p-2"
+            disabled={isLoading}
+          >
+            <X size={20} />
+          </button>
+        </div>
+
+        {/* Content */}
+        <div className="p-6">
+          <p className="text-[var(--color-neo-text-secondary)] mb-6">
+            {message}
+          </p>
+
+          {/* Actions */}
+          <div className="flex justify-end gap-3">
+            <button
+              onClick={onCancel}
+              className="neo-btn"
+              disabled={isLoading}
+            >
+              {cancelLabel}
+            </button>
+            <button
+              onClick={onConfirm}
+              className={`neo-btn ${colors.button}`}
+              disabled={isLoading}
+            >
+              {isLoading ? 'Deleting...' : confirmLabel}
+            </button>
+          </div>
+        </div>
+      </div>
+    </div>
+  )
+}