feat(web): add player name, freeform input, and unified settings modal

- Player name: stored in localStorage, injected into Architect/Writer/InsertBeat
  prompts so NPCs address the player by name, displayed in dialogue UI
- Freeform input: compact button at choice nodes expands to text input, LLM
  classifier routes to insert-beat (interactive NPC response) or change-scene
- SettingsModal: unified panel merging player name, voice toggle (with
  collapsible TTS key section), replacing the old TtsKeyModal
- Insert-beat upgrade: prompt now requires NPC reaction when characters are
  present, shared by both freeform and Vision paths
- IME guard: isComposing check on freeform input to prevent CJK mid-composition
  submission

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/api/classify-freeform/route.ts

@@ -0,0 +1,31 @@
+import { classifyFreeform } from "@infiplot/engine";
+import type { FreeformClassifyRequest } from "@infiplot/types";
+import { NextResponse } from "next/server";
+import { loadEngineConfig } from "@/lib/config";
+
+export const runtime = "nodejs";
+
+export async function POST(req: Request) {
+  let body: FreeformClassifyRequest;
+  try {
+    body = (await req.json()) as FreeformClassifyRequest;
+  } catch {
+    return NextResponse.json({ error: "Invalid JSON" }, { status: 400 });
+  }
+
+  if (!body.session || !body.freeformText?.trim()) {
+    return NextResponse.json(
+      { error: "session and freeformText are required" },
+      { status: 400 },
+    );
+  }
+
+  try {
+    const config = loadEngineConfig();
+    const result = await classifyFreeform(config, body);
+    return NextResponse.json(result);
+  } catch (err) {
+    const message = err instanceof Error ? err.message : "Unknown error";
+    return NextResponse.json({ error: message }, { status: 500 });
+  }
+}