fix: handle telegram: prefix in resolveTelegramTargetChatType

When using inlineButtons="dm" or "group" scope, the validation check
resolveTelegramTargetChatType() failed for numeric chat IDs because
normalizeTelegramMessagingTarget() adds a "telegram:" prefix during
target resolution.

For example, target "5232990709" becomes "telegram:5232990709" after
normalization, but the regex /^-?\d+$/ expects a pure numeric string.

The fix strips the telegram: prefix before checking the numeric pattern.

Adds tests for resolveTelegramTargetChatType with various input formats.

src/telegram/inline-buttons.test.ts

@@ -0,0 +1,31 @@
+import { describe, expect, it } from "vitest";
+
+import { resolveTelegramTargetChatType } from "./inline-buttons.js";
+
+describe("resolveTelegramTargetChatType", () => {
+  it("returns 'direct' for positive numeric IDs", () => {
+    expect(resolveTelegramTargetChatType("5232990709")).toBe("direct");
+    expect(resolveTelegramTargetChatType("123456789")).toBe("direct");
+  });
+
+  it("returns 'group' for negative numeric IDs", () => {
+    expect(resolveTelegramTargetChatType("-123456789")).toBe("group");
+    expect(resolveTelegramTargetChatType("-1001234567890")).toBe("group");
+  });
+
+  it("handles telegram: prefix from normalizeTelegramMessagingTarget", () => {
+    expect(resolveTelegramTargetChatType("telegram:5232990709")).toBe("direct");
+    expect(resolveTelegramTargetChatType("telegram:-123456789")).toBe("group");
+    expect(resolveTelegramTargetChatType("TELEGRAM:5232990709")).toBe("direct");
+  });
+
+  it("returns 'unknown' for usernames", () => {
+    expect(resolveTelegramTargetChatType("@username")).toBe("unknown");
+    expect(resolveTelegramTargetChatType("telegram:@username")).toBe("unknown");
+  });
+
+  it("returns 'unknown' for empty strings", () => {
+    expect(resolveTelegramTargetChatType("")).toBe("unknown");
+    expect(resolveTelegramTargetChatType("   ")).toBe("unknown");
+  });
+});