Problem
Currently, the logging.FatalHook unconditionally triggers telemetry collection whenever the CLI encounters a fatal error. This introduces two significant risks:

1. Re-entrancy/Deadlocks: If the telemetry collector itself encounters an error while gathering metrics (for instance, failing to rename or read a packer module), it can trigger another logging.Fatal() call. This recursive loop can lead to deadlocks or redundant executions.
2. Concurrent Duplicates: If multiple goroutines experience a fatal error simultaneously, they will both trigger the FatalHook at the same time, leading to duplicate payload generation and concurrent uploads to Clearcut.

Solution
This PR introduces a thread-safe atomic flag to guarantee that telemetry is flushed exactly once per CLI execution, regardless of concurrency or re-entrant fatal calls.

Changes

• cmd/root.go: Added telemetryFlushed atomic.Bool to serve as a 2-state flag for whether the telemetry event is flushed or not.
• cmd/root.go: Wrapped the telemetry execution inside the logging.FatalHook with if telemetryFlushed.CompareAndSwap(false, true).
• cmd/root_test.go: Added the TestFatalHook_ConcurrencyAndReentrancy unit test. This test spawns multiple concurrent goroutines to simulate race conditions and verifies that the telemetry hook behaves safely under load.

Rationale
Using an atomic.Bool with CompareAndSwap is superior to using standard locking mechanisms (like sync.Mutex or sync.Once) for this specific issue. Atomic operations are non-blocking; if a recursive call or a concurrent goroutine reaches the hook, it immediately evaluates to false and skips the block without waiting, safely proceeding to termination.

Advantages

• Prevents Duplicate Events: Ensures Clearcut analytics only receive one payload per execution.
• Safe CLI Termination: Eliminates the risk of deadlocks from infinite recursive logging.Fatal loops during failure handling.
• Ergonomic Types: Utilizing atomic.Bool expresses the intent clearly and avoids the error-prone usage of generic integer-based atomics.