feat: terminal-native torrent discovery TUI

Curated, multi-source torrent search and download from the terminal:
concurrent search across built-in sources with streamed, source-tagged
results; a download-only webtorrent engine with true pause/resume and
restart recovery; magnet paste; and a calm Ink + React TUI. No indexer
server, no setup.

src/ui/components/TextField.tsx

@@ -0,0 +1,139 @@
+import { useState } from "react";
+import { Text, useInput } from "ink";
+
+export interface TextFieldProps {
+  isDisabled?: boolean;
+  defaultValue?: string;
+  placeholder?: string;
+  onChange?: (value: string) => void;
+  onSubmit?: (value: string) => void;
+}
+
+interface Edit {
+  value: string;
+  cursor: number;
+}
+
+export function deleteBefore(value: string, cursor: number): Edit {
+  if (cursor === 0) return { value, cursor };
+  return {
+    value: value.slice(0, cursor - 1) + value.slice(cursor),
+    cursor: cursor - 1,
+  };
+}
+
+export function deleteWordBefore(value: string, cursor: number): Edit {
+  let i = cursor;
+  while (i > 0 && value[i - 1] === " ") i--;
+  while (i > 0 && value[i - 1] !== " ") i--;
+  return { value: value.slice(0, i) + value.slice(cursor), cursor: i };
+}
+
+export function killToEnd(value: string, cursor: number): Edit {
+  return { value: value.slice(0, cursor), cursor };
+}
+
+export function insertAt(value: string, cursor: number, text: string): Edit {
+  return {
+    value: value.slice(0, cursor) + text + value.slice(cursor),
+    cursor: cursor + text.length,
+  };
+}
+
+const CURSOR = " ";
+
+export function TextField({
+  isDisabled = false,
+  defaultValue = "",
+  placeholder = "",
+  onChange,
+  onSubmit,
+}: TextFieldProps) {
+  const [value, setValue] = useState(defaultValue);
+  const [cursor, setCursor] = useState(defaultValue.length);
+
+  function apply(next: Edit): void {
+    setValue(next.value);
+    setCursor(Math.max(0, Math.min(next.value.length, next.cursor)));
+    if (next.value !== value) onChange?.(next.value);
+  }
+
+  useInput(
+    (input, key) => {
+      if (key.upArrow || key.downArrow || key.tab || (key.ctrl && input === "c"))
+        return;
+
+      if (key.return) {
+        onSubmit?.(value);
+        return;
+      }
+
+      if (key.ctrl) {
+        switch (input) {
+          case "u":
+            apply({ value: "", cursor: 0 });
+            return;
+          case "w":
+            apply(deleteWordBefore(value, cursor));
+            return;
+          case "k":
+            apply(killToEnd(value, cursor));
+            return;
+          case "a":
+            setCursor(0);
+            return;
+          case "e":
+            setCursor(value.length);
+            return;
+          default:
+            return;
+        }
+      }
+
+      if (key.leftArrow) {
+        setCursor(Math.max(0, cursor - 1));
+        return;
+      }
+      if (key.rightArrow) {
+        setCursor(Math.min(value.length, cursor + 1));
+        return;
+      }
+      if (key.backspace || key.delete) {
+        apply(deleteBefore(value, cursor));
+        return;
+      }
+      if (key.meta || !input) return;
+      const text = input.replace(/\x1b?\[<\d+;\d+;\d+[Mm]/g, "");
+      if (!text) return;
+      apply(insertAt(value, cursor, text));
+    },
+    { isActive: !isDisabled },
+  );
+
+  if (isDisabled) {
+    return value ? <Text>{value}</Text> : <Text dimColor>{placeholder}</Text>;
+  }
+
+  if (value.length === 0) {
+    if (placeholder) {
+      return (
+        <Text>
+          <Text inverse>{placeholder[0]}</Text>
+          <Text dimColor>{placeholder.slice(1)}</Text>
+        </Text>
+      );
+    }
+    return <Text inverse>{CURSOR}</Text>;
+  }
+
+  const before = value.slice(0, cursor);
+  const atChar = value[cursor] ?? CURSOR;
+  const after = cursor < value.length ? value.slice(cursor + 1) : "";
+  return (
+    <Text>
+      {before}
+      <Text inverse>{atChar}</Text>
+      {after}
+    </Text>
+  );
+}