refactor(slack): centralize target parsing

src/slack/send.ts

@@ -7,6 +7,7 @@ import { loadWebMedia } from "../web/media.js";
 import type { SlackTokenSource } from "./accounts.js";
 import { resolveSlackAccount } from "./accounts.js";
 import { markdownToSlackMrkdwnChunks } from "./format.js";
+import { parseSlackTarget } from "./targets.js";
 import { resolveSlackBotToken } from "./token.js";
 
 const SLACK_TEXT_LIMIT = 4000;
@@ -57,38 +58,11 @@ function resolveToken(params: {
 }
 
 function parseRecipient(raw: string): SlackRecipient {
-  const trimmed = raw.trim();
-  if (!trimmed) {
+  const target = parseSlackTarget(raw);
+  if (!target) {
     throw new Error("Recipient is required for Slack sends");
   }
-  const mentionMatch = trimmed.match(/^<@([A-Z0-9]+)>$/i);
-  if (mentionMatch) {
-    return { kind: "user", id: mentionMatch[1] };
-  }
-  if (trimmed.startsWith("user:")) {
-    return { kind: "user", id: trimmed.slice("user:".length) };
-  }
-  if (trimmed.startsWith("channel:")) {
-    return { kind: "channel", id: trimmed.slice("channel:".length) };
-  }
-  if (trimmed.startsWith("slack:")) {
-    return { kind: "user", id: trimmed.slice("slack:".length) };
-  }
-  if (trimmed.startsWith("@")) {
-    const candidate = trimmed.slice(1);
-    if (!/^[A-Z0-9]+$/i.test(candidate)) {
-      throw new Error("Slack DMs require a user id (use user:<id> or <@id>)");
-    }
-    return { kind: "user", id: candidate };
-  }
-  if (trimmed.startsWith("#")) {
-    const candidate = trimmed.slice(1);
-    if (!/^[A-Z0-9]+$/i.test(candidate)) {
-      throw new Error("Slack channels require a channel id (use channel:<id>)");
-    }
-    return { kind: "channel", id: candidate };
-  }
-  return { kind: "channel", id: trimmed };
+  return { kind: target.kind, id: target.id };
 }
 
 async function resolveChannelId(