🧩 Issue #6: Add unit test for multiple independent fire commands in sequence

Add a unit test to `controller.rs` that verifies support for **multiple fire commands in sequence** — e.g., schedule `Fire(1.0)`, then after it completes, schedule `Fire(2.0)`. Both should trigger independently.

### Goals

- ✅ Ensure two separate fire events result in `"firing now!"` twice
- ✅ Confirm that commands are not overwritten or canceled unintentionally
- ✅ Use atomic counter or similar mechanism to assert correct behavior
- ✅ Keep test duration short (e.g., < 3s) using `sleep(0.05)` style timing

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| Field | Value |
|-------------|-------------|
| Status | Ready |
| Type | Test |
| Area | Controller |
| Priority | Medium |
| Branch | TBD |
| Blocks | |
| Blocked By | |
| Related To | #1 |
| Upstream | |