Summary

• Remove the hardcoded 2-second sleep in exec_users_list() by implementing proper synchronisation between the main thread and TDLib's update thread
• TelegramClient::start() now blocks until TDLib signals it's ready (via authorization state change)
• Add comprehensive tests with mocks for the initialization synchronisation mechanism

Changes

src/tg/client.cpp

• Add init_promise_, init_future_, and init_completed_ members to Impl
• Add complete_initialization() helper that safely signals the promise
• Add wait_initialized() method that blocks until TDLib is ready (with 30s timeout)
• Modify process_authorization_state() to call complete_initialization() on meaningful state transitions (WAIT_PHONE, WAIT_CODE, WAIT_PASSWORD, or READY)
• Update TelegramClient::start() to call wait_initialized()

src/ctl/users.cpp

• Remove the 2-second std::this_thread::sleep_for() workaround
• Remove now-unused <chrono> and <thread> includes

tests/tg/client_init_test.cpp (new)

• Add MockInitSynchronizer class that mirrors the exact synchronisation logic
• Add 11 tests covering: blocking behaviour, timeout, thread-safety, stress testing, Task integration, exception propagation

Test plan

• All 122 tests pass (including 11 new client init tests)
• tg-fuse users --list executes immediately without 2-second delay
• Works correctly when already authenticated (fast path)
• Works correctly when not authenticated (returns error promptly)