feat: count all platforms in multi-link posts

- add PlatformSet to track unique platforms per post
- detectAllPlatformsFromRecord returns all platforms found
- posts with multiple platform links now count each platform
- remove old single-platform detection function

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

src/feed/filter.zig

···
     return null;
 }
 
-/// detect platform from post record (checks facets and embeds)
-pub fn detectPlatformFromRecord(record: Record) ?stats.Platform {
+/// simple text-based check for music links (used for backfill)
+pub fn textContainsMusicLink(text: []const u8) bool {
+    for (music_domains) |domain| {
+        if (mem.indexOf(u8, text, domain) != null) return true;
+    }
+    return false;
+}
+
+/// set of platforms found in a post (deduplicated)
+pub const PlatformSet = struct {
+    soundcloud: bool = false,
+    bandcamp: bool = false,
+    spotify: bool = false,
+    plyr: bool = false,
+    apple: bool = false,
+
+    pub fn add(self: *PlatformSet, p: stats.Platform) void {
+        switch (p) {
+            .soundcloud => self.soundcloud = true,
+            .bandcamp => self.bandcamp = true,
+            .spotify => self.spotify = true,
+            .plyr => self.plyr = true,
+            .apple => self.apple = true,
+        }
+    }
+
+    pub fn isEmpty(self: PlatformSet) bool {
+        return !self.soundcloud and !self.bandcamp and !self.spotify and !self.plyr and !self.apple;
+    }
+
+    pub fn count(self: PlatformSet) u8 {
+        var n: u8 = 0;
+        if (self.soundcloud) n += 1;
+        if (self.bandcamp) n += 1;
+        if (self.spotify) n += 1;
+        if (self.plyr) n += 1;
+        if (self.apple) n += 1;
+        return n;
+    }
+};
+
+/// detect all unique platforms in a post record
+pub fn detectAllPlatformsFromRecord(record: Record) PlatformSet {
+    var result = PlatformSet{};
     const val: json.Value = .{ .object = record };
 
     // check embed.external.uri
     if (zat.json.getString(val, "embed.external.uri")) |uri| {
-        if (detectPlatform(uri)) |p| return p;
+        if (detectPlatform(uri)) |p| result.add(p);
     }
 
     // check facets
-    const facets = zat.json.getArray(val, "facets") orelse return null;
+    const facets = zat.json.getArray(val, "facets") orelse return result;
     for (facets) |facet| {
         const features = zat.json.getArray(facet, "features") orelse continue;
         for (features) |feature| {
             const uri = zat.json.getString(feature, "uri") orelse continue;
-            if (detectPlatform(uri)) |p| return p;
+            if (detectPlatform(uri)) |p| result.add(p);
         }
     }
 
-    return null;
-}
-
-/// simple text-based check for music links (used for backfill)
-pub fn textContainsMusicLink(text: []const u8) bool {
-    for (music_domains) |domain| {
-        if (mem.indexOf(u8, text, domain) != null) return true;
-    }
-    return false;
+    return result;
 }
 
 // -----------------------------------------------------------------------------
···
     try testing.expect(!textContainsMusicLink("just vibing to some tunes"));
     try testing.expect(!textContainsMusicLink(""));
 }
+
+test "PlatformSet" {
+    const testing = std.testing;
+
+    var set = PlatformSet{};
+    try testing.expect(set.isEmpty());
+    try testing.expectEqual(0, set.count());
+
+    set.add(.spotify);
+    try testing.expect(!set.isEmpty());
+    try testing.expectEqual(1, set.count());
+    try testing.expect(set.spotify);
+    try testing.expect(!set.soundcloud);
+
+    // adding same platform again doesn't change count
+    set.add(.spotify);
+    try testing.expectEqual(1, set.count());
+
+    // adding different platforms
+    set.add(.apple);
+    set.add(.bandcamp);
+    try testing.expectEqual(3, set.count());
+    try testing.expect(set.spotify);
+    try testing.expect(set.apple);
+    try testing.expect(set.bandcamp);
+    try testing.expect(!set.soundcloud);
+    try testing.expect(!set.plyr);
+}

src/jetstream.zig

···
 
         stats.get().recordMatch();
 
-        // track platform
-        if (filter.detectPlatformFromRecord(post_record.object)) |platform| {
-            stats.get().recordPlatform(platform);
-        }
+        // track all platforms in post
+        const platforms = filter.detectAllPlatformsFromRecord(post_record.object);
+        const s = stats.get();
+        if (platforms.soundcloud) s.recordPlatform(.soundcloud);
+        if (platforms.bandcamp) s.recordPlatform(.bandcamp);
+        if (platforms.spotify) s.recordPlatform(.spotify);
+        if (platforms.plyr) s.recordPlatform(.plyr);
+        if (platforms.apple) s.recordPlatform(.apple);
 
         std.debug.print("added: {s}\n", .{at_uri.string});
     }