feat: add cursor-based pagination for following/followers commands

Add pagination support to `bird following` and `bird followers` commands,
similar to existing pagination in search/bookmarks/likes.

Changes:
- Add `cursor` parameter to `getFollowing()` and `getFollowers()` client methods
- Return `nextCursor` in `FollowingResult` for pagination continuation
- Add `--cursor <cursor>` CLI option for manual pagination
- Add `--all` CLI flag to automatically fetch all pages
- Add `--max-pages <number>` option to limit pages when using --all
- Add input validation for --max-pages (requires --all or --cursor)
- Add deduplication using Set to prevent duplicate users
- Add 1-second delay between pages to avoid overwhelming the API
- Update `-n/--count` description to clarify it's per-page
- Add unit tests for cursor parameter and nextCursor response

Usage examples:
  # Fetch first page (default 20 users)
  bird following

  # Fetch with specific page size
  bird following -n 50

  # Use cursor for next page
  bird following --cursor "CURSOR_FROM_PREVIOUS"

  # Fetch ALL following users automatically (with rate limiting)
  bird following --all --json

  # Limit to first 5 pages
  bird following --all --max-pages 5

  # Same options work for followers
  bird followers --all

Note: REST API fallback does not support cursor pagination.

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

Co-Authored-By: Claude Opus 4.5 <[email protected]>

tests/twitter-client.following-likes.test.ts

@@ -280,6 +280,160 @@ describe('TwitterClient following/followers', () => {
     expect(urls[1]).toContain('/Followers?');
     expect(urls[2]).toContain('/followers/list.json?');
   });
+
+  it('passes cursor parameter to following API and returns nextCursor', async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        data: {
+          user: {
+            result: {
+              timeline: {
+                timeline: {
+                  instructions: [
+                    {
+                      type: 'TimelineAddEntries',
+                      entries: [
+                        {
+                          content: {
+                            itemContent: {
+                              user_results: {
+                                result: makeUserResult('1', 'alpha', 'Alpha'),
+                              },
+                            },
+                          },
+                        },
+                        {
+                          content: {
+                            cursorType: 'Bottom',
+                            value: 'next-cursor-abc123',
+                          },
+                        },
+                      ],
+                    },
+                  ],
+                },
+              },
+            },
+          },
+        },
+      }),
+    });
+
+    const client = new TwitterClient({ cookies: validCookies });
+    const clientPrivate = client as unknown as TwitterClient & { getFollowingQueryIds: () => Promise<string[]> };
+    clientPrivate.getFollowingQueryIds = async () => ['test'];
+
+    const result = await client.getFollowing('123', 20, 'prev-cursor-xyz');
+
+    expect(result.success).toBe(true);
+    expect(result.users?.length).toBe(1);
+    expect(result.nextCursor).toBe('next-cursor-abc123');
+
+    // Verify cursor was passed in the request
+    const [url] = mockFetch.mock.calls[0];
+    const parsedVars = JSON.parse(new URL(url as string).searchParams.get('variables') as string);
+    expect(parsedVars.cursor).toBe('prev-cursor-xyz');
+  });
+
+  it('passes cursor parameter to followers API and returns nextCursor', async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        data: {
+          user: {
+            result: {
+              timeline: {
+                timeline: {
+                  instructions: [
+                    {
+                      entries: [
+                        {
+                          content: {
+                            itemContent: {
+                              user_results: {
+                                result: makeUserResult('9', 'beta', 'Beta'),
+                              },
+                            },
+                          },
+                        },
+                        {
+                          content: {
+                            cursorType: 'Bottom',
+                            value: 'followers-next-cursor',
+                          },
+                        },
+                      ],
+                    },
+                  ],
+                },
+              },
+            },
+          },
+        },
+      }),
+    });
+
+    const client = new TwitterClient({ cookies: validCookies });
+    const clientPrivate = client as unknown as TwitterClient & { getFollowersQueryIds: () => Promise<string[]> };
+    clientPrivate.getFollowersQueryIds = async () => ['test'];
+
+    const result = await client.getFollowers('456', 50, 'my-cursor');
+
+    expect(result.success).toBe(true);
+    expect(result.users?.[0].username).toBe('beta');
+    expect(result.nextCursor).toBe('followers-next-cursor');
+
+    // Verify cursor was passed in the request
+    const [url] = mockFetch.mock.calls[0];
+    const parsedVars = JSON.parse(new URL(url as string).searchParams.get('variables') as string);
+    expect(parsedVars.cursor).toBe('my-cursor');
+  });
+
+  it('returns undefined nextCursor when no cursor in response', async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        data: {
+          user: {
+            result: {
+              timeline: {
+                timeline: {
+                  instructions: [
+                    {
+                      entries: [
+                        {
+                          content: {
+                            itemContent: {
+                              user_results: {
+                                result: makeUserResult('1', 'only', 'Only'),
+                              },
+                            },
+                          },
+                        },
+                      ],
+                    },
+                  ],
+                },
+              },
+            },
+          },
+        },
+      }),
+    });
+
+    const client = new TwitterClient({ cookies: validCookies });
+    const clientPrivate = client as unknown as TwitterClient & { getFollowingQueryIds: () => Promise<string[]> };
+    clientPrivate.getFollowingQueryIds = async () => ['test'];
+
+    const result = await client.getFollowing('123', 20);
+
+    expect(result.success).toBe(true);
+    expect(result.nextCursor).toBeUndefined();
+  });
 });
 
 describe('TwitterClient likes', () => {