cleanup: remove dead fetchOnlyFollowerCount + clarify profile inferred type

Two related artifacts left over from the avatar/banner GQL refactor
in 4.6.20:

- fetchOnlyFollowerCount was an early standalone helper from the
  iteration where Helix supplied core profile fields and a separate
  public-GQL roundtrip pulled just the follower count. The 4.6.19
  rewrite folded all of that into a single public-GQL query, so the
  helper has no callers. Removed.

- streamFromPublic was typed via
  `Awaited<ReturnType<typeof fetchPublicStreamerProfile>> extends ...`
  conditional inference because the inline stream shape was anonymous.
  That worked but read like a riddle. Hoisted the inline shapes to
  two named interfaces (PublicStreamInfo + PublicStreamerProfileResult)
  so the function signature is explicit and the local var is just
  `PublicStreamInfo | null`. Same type, an order of magnitude more
  obvious to anyone reading.

Both changes are zero-runtime-behavior; tests confirm.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/main.ts

@@ -2410,15 +2410,24 @@ interface PublicProfileQueryResult {
     } | null;
 }
 
-async function fetchPublicStreamerProfile(login: string): Promise<{
+interface PublicStreamerProfileResult {
     displayName: string;
     avatarUrl: string;
     bannerUrl: string;
     description: string;
     broadcasterType: '' | 'partner' | 'affiliate';
     followerCount: number | null;
-    stream: { previewUrl: string; viewers: number | null; title: string | null; game: string | null } | null;
+    stream: PublicStreamInfo | null;
-} | null> {
+}
+
+interface PublicStreamInfo {
+    previewUrl: string;
+    viewers: number | null;
+    title: string | null;
+    game: string | null;
+}
+
+async function fetchPublicStreamerProfile(login: string): Promise<PublicStreamerProfileResult | null> {
     // Same query also pulls bannerImageURL and the current stream's
     // preview + viewer count when live — saves a separate roundtrip.
     const data = await fetchPublicTwitchGql<PublicProfileQueryResult>(
@@ -2467,15 +2476,6 @@ async function fetchPublicStreamerProfile(login: string): Promise<{
     };
 }
 
-async function fetchOnlyFollowerCount(login: string): Promise<number | null> {
-    const data = await fetchPublicTwitchGql<PublicProfileQueryResult>(
-        `query($login: String!) { user(login: $login) { followers { totalCount } } }`,
-        { login }
-    );
-    const cnt = data?.user?.followers?.totalCount;
-    return typeof cnt === 'number' ? cnt : null;
-}
-
 async function getStreamerProfile(login: string, forceRefresh = false): Promise<StreamerProfile | null> {
     const normalized = normalizeLogin(login);
     if (!normalized) return null;
@@ -2502,7 +2502,7 @@ async function getStreamerProfile(login: string, forceRefresh = false): Promise<
         let bannerUrl = '';
         let description = '';
         let broadcasterType: '' | 'partner' | 'affiliate' = '';
-        let streamFromPublic: Awaited<ReturnType<typeof fetchPublicStreamerProfile>> extends infer R ? (R extends null ? null : R extends { stream: infer S } ? S : null) : null = null;
+        let streamFromPublic: PublicStreamInfo | null = null;
         let followerCountFromPublic: number | null = null;
 
         const publicProfile = await fetchPublicStreamerProfile(normalized);