feat: integrate n+1 target highlighting

- Merge feature branch changes for n+1 target-only highlight flow

- Extend merged token model and token-merger to mark exactly-one unknown targets

- Thread n+1 candidate metadata through tokenizer and config systems

- Update subtitle renderer/state to route configured colors and new token class

- Resolve merge conflicts in core service tests, including subtitle and subsync behavior

src/config/config.test.ts

@@ -186,6 +186,63 @@ test("accepts valid ankiConnect n+1 match mode values", () => {
   assert.equal(config.ankiConnect.nPlusOne.matchMode, "surface");
 });
 
+test("validates ankiConnect n+1 color values", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "nPlusOne": {
+          "nPlusOne": "not-a-color",
+          "knownWord": 123
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+  const warnings = service.getWarnings();
+
+  assert.equal(
+    config.ankiConnect.nPlusOne.nPlusOne,
+    DEFAULT_CONFIG.ankiConnect.nPlusOne.nPlusOne,
+  );
+  assert.equal(
+    config.ankiConnect.nPlusOne.knownWord,
+    DEFAULT_CONFIG.ankiConnect.nPlusOne.knownWord,
+  );
+  assert.ok(
+    warnings.some((warning) => warning.path === "ankiConnect.nPlusOne.nPlusOne"),
+  );
+  assert.ok(
+    warnings.some((warning) => warning.path === "ankiConnect.nPlusOne.knownWord"),
+  );
+});
+
+test("accepts valid ankiConnect n+1 color values", () => {
+  const dir = makeTempDir();
+  fs.writeFileSync(
+    path.join(dir, "config.jsonc"),
+    `{
+      "ankiConnect": {
+        "nPlusOne": {
+          "nPlusOne": "#c6a0f6",
+          "knownWord": "#a6da95"
+        }
+      }
+    }`,
+    "utf-8",
+  );
+
+  const service = new ConfigService(dir);
+  const config = service.getConfig();
+
+  assert.equal(config.ankiConnect.nPlusOne.nPlusOne, "#c6a0f6");
+  assert.equal(config.ankiConnect.nPlusOne.knownWord, "#a6da95");
+});
+
 test("supports legacy ankiConnect.behavior N+1 settings as fallback", () => {
   const dir = makeTempDir();
   fs.writeFileSync(
@@ -268,5 +325,8 @@ test("template generator includes known keys", () => {
   assert.match(output, /"ankiConnect":/);
   assert.match(output, /"websocket":/);
   assert.match(output, /"youtubeSubgen":/);
+  assert.match(output, /"nPlusOne"\s*:\s*\{/);
+  assert.match(output, /"nPlusOne": "#c6a0f6"/);
+  assert.match(output, /"knownWord": "#a6da95"/);
   assert.match(output, /auto-generated from src\/config\/definitions.ts/);
 });