mv: do not panic when debug output write fails

[R0B2133]

Summary

• replace mv's direct debug and verbose println! calls with fallible stdout writes
• report the first stdout write failure as a localized diagnostic, continue filesystem operations, and return a failure status
• add Linux /dev/full regression coverage for the exact issue and for multi-source skip/continue behavior

Fixes #11246

Testing

• cargo fmt --all --check
• cargo build --no-default-features --features mv
• cargo test --no-default-features --features mv --test tests test_mv (91 passed, 0 failed on Windows)
• cargo clippy -p uu_mv --all-targets
• deterministic Windows closed-pipe regression harness covering both new failure-path cases

The two new /dev/full tests are Linux-only and could not be run on this Windows host; they are included for Linux CI validation.

[codspeed-hq]

Merging this PR will degrade performance by 18.34%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 346 untouched benchmarks
⏩ 46 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	df_with_path	571.4 µs	699.8 µs	-18.34%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing R0B2133:fix/mv-debug-stdout-write-error-11246 (4869632) with main (21d4e96)}

Footnotes

1. 46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩