Add fault-injection tests for flashing failures

[ashishsinghbora]

Problem Statement

FlashCore needs predictable behavior when storage operations fail during a real flash.

Proposed Solution / Enhancement

Use the fault-injecting BlockDevice to simulate:

• USB disconnect
• Timeout
• Short read
• Short write
• Read failure
• Write failure
• Flush failure
• GPT failure
• FAT failure
• Verification mismatch

For every failure, verify that FlashCore:

• Stops safely
• Reports the correct error
• Does not report success
• Releases resources correctly

Architectural Layer Impacted

Flash Engine / Block Device / Error Handling / Verification

Alternatives Considered

Testing only successful flashes does not prove that the application is safe during failure.