feat: post tags (Lemmy v1 + PieFed) (#40)

Surface per-post tags on `PostView.tags` as a portable `PostTag[]` shape
(`{ name, display_name?, color? }`) so consumers can render them
uniformly across backends.

- Lemmy v1: maps each `CommunityTag` on `PostView.tags`. `color` is the
  palette slot (e.g. `"color03"`).
- PieFed: maps `PostView.flair_list[]` (CommunityFlair). `color` is the
  hex `background_color` (e.g. `"#a91b9c"`).
- Lemmy v0: `tags: []`.

`color` is opaque to threadiverse — consumers either render it directly
(hex) or resolve it from a palette (Lemmy v1). The minimal shape skips
v1-specific housekeeping (`id`, `ap_id`, `published_at`, `deleted`,
`community_id`) since they don't have PieFed analogs and aren't useful
for view-only rendering; mutation APIs can grow their own richer types
later.

Author: aeharding

src/providers/lemmyv0/compat.ts

@@ -636,6 +636,7 @@ export function toPostView(v: LemmyV0.PostView): types.PostView {
     read: v.read,
     saved: v.saved,
     subscribed: v.subscribed,
+    tags: [],
     unread_comments: v.unread_comments,
   };
 }

src/providers/piefed/compat.ts

@@ -255,6 +255,10 @@ export function toPostView(
     read: v.read,
     saved: v.saved,
     subscribed: toSubscribedType(v.subscribed),
+    tags: (v.flair_list ?? []).map((f) => ({
+      color: f.background_color,
+      name: f.flair_title,
+    })),
     unread_comments: v.counts.comments,
   };
 }

src/schemas/PostTag.ts

@@ -0,0 +1,19 @@
+import { z } from "zod/v4-mini";
+
+/**
+ * A tag attached to a post.
+ *
+ * - Lemmy v1: maps from `CommunityTag` (mod-curated, palette color slot like
+ *   `"color03"`).
+ * - PieFed: maps from `CommunityFlair` applied to the post (hex `color`
+ *   like `"#a91b9c"`).
+ * - Lemmy v0: not supported (empty array).
+ *
+ * `color` is opaque to threadiverse — consumers either render it directly
+ * (hex) or look it up in a palette (Lemmy v1 slot keys).
+ */
+export const PostTag = z.object({
+  color: z.optional(z.string()),
+  display_name: z.optional(z.string()),
+  name: z.string(),
+});

src/schemas/PostView.ts

@@ -4,6 +4,7 @@ import { Community } from "./Community";
 import { Person } from "./Person";
 import { Post } from "./Post";
 import { PostNotificationsMode } from "./PostNotificationsMode";
+import { PostTag } from "./PostTag";
 import { SubscribedType } from "./SubscribedType";
 import { Vote } from "./Vote";
 
@@ -22,5 +23,6 @@ export const PostView = z.object({
   read: z.boolean(),
   saved: z.boolean(),
   subscribed: SubscribedType,
+  tags: z.array(PostTag),
   unread_comments: z.number(),
 });

src/schemas/index.ts

@@ -36,6 +36,7 @@ export * from "./Post";
 export * from "./PostNotificationsMode";
 export * from "./PostReport";
 export * from "./PostReportView";
+export * from "./PostTag";
 export * from "./PostView";
 export * from "./PrivateMessage";
 export * from "./PrivateMessageView";

src/types/index.ts

@@ -83,6 +83,7 @@ export type PostNotificationsMode = z.infer<
 >;
 export type PostReport = z.infer<typeof schemas.PostReport>;
 export type PostReportView = z.infer<typeof schemas.PostReportView>;
+export type PostTag = z.infer<typeof schemas.PostTag>;
 export type PostView = z.infer<typeof schemas.PostView>;
 export type PrivateMessage = z.infer<typeof schemas.PrivateMessage>;
 export type PrivateMessageView = z.infer<typeof schemas.PrivateMessageView>;