feat: add FileInput primitive — drag-and-drop file picker

Dashed-border dropzone with icon, filename display, clear button,
and imperative handle (file/clear). Replaces native file inputs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/design-system/primitives/FileInput/FileInput.module.css

@@ -0,0 +1,64 @@
+.wrap {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 10px 12px;
+  border: 1.5px dashed var(--border);
+  border-radius: var(--radius-sm);
+  background: var(--bg-inset);
+  cursor: pointer;
+  transition: border-color 0.15s, background 0.15s;
+}
+
+.wrap:hover {
+  border-color: var(--text-muted);
+}
+
+.dragOver {
+  border-color: var(--amber);
+  background: var(--amber-bg);
+}
+
+.icon {
+  color: var(--text-faint);
+  flex-shrink: 0;
+  line-height: 0;
+}
+
+.label {
+  font-family: var(--font-body);
+  font-size: 12px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.placeholder {
+  color: var(--text-faint);
+}
+
+.fileName {
+  color: var(--text-primary);
+}
+
+.clearBtn {
+  margin-left: auto;
+  flex-shrink: 0;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 20px;
+  height: 20px;
+  border: none;
+  background: none;
+  color: var(--text-muted);
+  cursor: pointer;
+  border-radius: var(--radius-sm);
+  padding: 0;
+  transition: color 0.1s, background 0.1s;
+}
+
+.clearBtn:hover {
+  color: var(--text-primary);
+  background: var(--bg-hover);
+}

src/design-system/primitives/FileInput/FileInput.tsx

@@ -0,0 +1,99 @@
+import styles from './FileInput.module.css'
+import { forwardRef, useRef, useState, useImperativeHandle, type ReactNode } from 'react'
+import { X } from 'lucide-react'
+
+export interface FileInputProps {
+  /** File type filter, e.g. ".pem,.crt,.cer" */
+  accept?: string
+  /** Icon rendered before the label */
+  icon?: ReactNode
+  /** Placeholder text when no file is selected */
+  placeholder?: string
+  /** Additional CSS class */
+  className?: string
+  /** Called when a file is selected or cleared */
+  onChange?: (file: File | null) => void
+}
+
+export interface FileInputHandle {
+  /** The currently selected File, or null */
+  file: File | null
+  /** Programmatically clear the selection */
+  clear: () => void
+}
+
+export const FileInput = forwardRef<FileInputHandle, FileInputProps>(
+  ({ accept, icon, placeholder = 'Drop file or click to browse', className, onChange }, ref) => {
+    const inputRef = useRef<HTMLInputElement>(null)
+    const [fileName, setFileName] = useState<string | null>(null)
+    const [dragOver, setDragOver] = useState(false)
+    const fileRef = useRef<File | null>(null)
+
+    function select(file: File | null) {
+      fileRef.current = file
+      setFileName(file?.name ?? null)
+      onChange?.(file)
+    }
+
+    function handleInputChange() {
+      select(inputRef.current?.files?.[0] ?? null)
+    }
+
+    function handleDrop(e: React.DragEvent) {
+      e.preventDefault()
+      setDragOver(false)
+      const file = e.dataTransfer.files[0]
+      if (file && inputRef.current) {
+        const dt = new DataTransfer()
+        dt.items.add(file)
+        inputRef.current.files = dt.files
+        select(file)
+      }
+    }
+
+    function handleClear(e: React.MouseEvent) {
+      e.stopPropagation()
+      if (inputRef.current) inputRef.current.value = ''
+      select(null)
+    }
+
+    useImperativeHandle(ref, () => ({
+      get file() { return fileRef.current },
+      clear() {
+        if (inputRef.current) inputRef.current.value = ''
+        select(null)
+      },
+    }))
+
+    const wrapClass = [styles.wrap, dragOver && styles.dragOver, className].filter(Boolean).join(' ')
+
+    return (
+      <div
+        className={wrapClass}
+        onClick={() => inputRef.current?.click()}
+        onDragOver={(e) => { e.preventDefault(); setDragOver(true) }}
+        onDragLeave={() => setDragOver(false)}
+        onDrop={handleDrop}
+      >
+        {icon && <span className={styles.icon}>{icon}</span>}
+        <span className={`${styles.label} ${fileName ? styles.fileName : styles.placeholder}`}>
+          {fileName ?? placeholder}
+        </span>
+        {fileName && (
+          <button type="button" className={styles.clearBtn} onClick={handleClear} aria-label="Clear file">
+            <X size={12} />
+          </button>
+        )}
+        <input
+          ref={inputRef}
+          type="file"
+          accept={accept}
+          onChange={handleInputChange}
+          style={{ display: 'none' }}
+        />
+      </div>
+    )
+  },
+)
+
+FileInput.displayName = 'FileInput'

src/design-system/primitives/index.ts

@@ -11,6 +11,8 @@ export { Collapsible } from './Collapsible/Collapsible'
 export { DateRangePicker } from './DateRangePicker/DateRangePicker'
 export { DateTimePicker } from './DateTimePicker/DateTimePicker'
 export { EmptyState } from './EmptyState/EmptyState'
+export { FileInput } from './FileInput/FileInput'
+export type { FileInputProps, FileInputHandle } from './FileInput/FileInput'
 export { FilterPill } from './FilterPill/FilterPill'
 export { FormField } from './FormField/FormField'
 export { InfoCallout } from './InfoCallout/InfoCallout'