Add #rss command family with LLM tags and summaries (v0.20.0)

#rss subcommands on the command channel: help / add <url> <name> /
remove <name> / tags / sources / get <name|#tag>. Sources are stored in
a new rss_sources table in the existing MESH_DB_PATH file (second
node:sqlite connection, case-insensitive names); feeds parsed with
fast-xml-parser (RSS 2.0 + Atom); AI tags and headline summaries via
injected LlmService.chat() with bounded maxTokens (50/200).

CommandService gains prefix registration so one handler owns the whole
#rss family while #ping stays an exact match; wired in CommandModule's
factory — still no constructor-level cycle, no forwardRef. One dead feed
does not sink a tag summary.

src/rss/rss.store.ts

@@ -0,0 +1,108 @@
+import { DatabaseSync } from 'node:sqlite';
+
+/** A stored RSS source; tags are a comma-separated string in the DB, split here. */
+export interface RssSource {
+  name: string;
+  url: string;
+  tags: string[];
+  createdAt: number;
+}
+
+/** Idempotent — safe to call on every open (the table lives in the shared MESH_DB_PATH file). */
+export function initRssTable(db: DatabaseSync): void {
+  db.exec(`CREATE TABLE IF NOT EXISTS rss_sources (
+    name TEXT PRIMARY KEY,
+    url TEXT NOT NULL,
+    tags TEXT NOT NULL DEFAULT '',
+    created_at INTEGER
+  )`);
+}
+
+/** CRUD for the rss_sources table. Names are matched case-insensitively everywhere. */
+export class RssStore {
+  constructor(private readonly db: DatabaseSync) {
+    initRssTable(db);
+  }
+
+  list(): RssSource[] {
+    const rows = this.db
+      .prepare(
+        'SELECT name, url, tags, created_at FROM rss_sources ORDER BY name',
+      )
+      .all() as {
+      name: string;
+      url: string;
+      tags: string;
+      created_at: number;
+    }[];
+    return rows.map((r) => ({
+      name: r.name,
+      url: r.url,
+      tags: splitTags(r.tags),
+      createdAt: r.created_at,
+    }));
+  }
+
+  /** Case-insensitive lookup by name. */
+  get(name: string): RssSource | undefined {
+    const row = this.db
+      .prepare(
+        'SELECT name, url, tags, created_at FROM rss_sources WHERE name = ? COLLATE NOCASE',
+      )
+      .get(name) as
+      | { name: string; url: string; tags: string; created_at: number }
+      | undefined;
+    return (
+      row && {
+        name: row.name,
+        url: row.url,
+        tags: splitTags(row.tags),
+        createdAt: row.created_at,
+      }
+    );
+  }
+
+  /** Case-insensitive duplicate check. */
+  exists(name: string): boolean {
+    const row = this.db
+      .prepare('SELECT 1 FROM rss_sources WHERE name = ? COLLATE NOCASE')
+      .get(name);
+    return row !== undefined;
+  }
+
+  add(source: { name: string; url: string; tags: string[] }): void {
+    this.db
+      .prepare(
+        'INSERT INTO rss_sources (name, url, tags, created_at) VALUES (?, ?, ?, ?)',
+      )
+      .run(source.name, source.url, joinTags(source.tags), Date.now());
+  }
+
+  /** Case-insensitive delete; true when a row was removed. */
+  remove(name: string): boolean {
+    const result = this.db
+      .prepare('DELETE FROM rss_sources WHERE name = ? COLLATE NOCASE')
+      .run(name);
+    return Number(result.changes) > 0;
+  }
+
+  /** All distinct tags across sources, sorted. */
+  allTags(): string[] {
+    const set = new Set<string>();
+    for (const source of this.list()) {
+      for (const tag of source.tags) set.add(tag);
+    }
+    return [...set].sort();
+  }
+}
+
+export function splitTags(raw: string): string[] {
+  return raw
+    .split(',')
+    .map((t) => t.trim())
+    .filter(Boolean);
+}
+
+export function joinTags(tags: string[]): string {
+  return tags.join(',');
+}