fix(rp2040): explain Windows synthetic volume errors

[zackees]

Summary

• classify Windows error 1392 from the RP-series BOOTSEL synthetic FAT volume
• preserve the original copy error while explicitly warning against chkdsk, repair, or formatting
• direct users to reconnect or use fbuild's managed picotool fallback with the documented WinUSB binding

Validation

• soldr cargo fmt --all -- --check
• soldr cargo test -p fbuild-deploy rp2040 (27 passed)
• soldr cargo clippy -p fbuild-deploy --all-targets -- -D warnings (passes; existing MSRV config warning only)
• clud-review: APPROVE
• attached stock Pico: rebuilt editable package and reproduced Windows error 1392; live fbuild output included the new safety diagnostic and then attempted managed picotool

Part of #1049.

Summary by CodeRabbit

• Bug Fixes
  • Improved UF2 deployment error messages on Windows when the BOOTSEL volume reports error 1392.
  • Added actionable guidance to retry in BOOTSEL mode or use the managed fallback tool.
  • Preserved general fallback guidance for other UF2 copy failures.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

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Review profile: CHILL

Plan: Pro

Run ID: f757c9d4-0865-481a-b07e-475318c10afb

📥 Commits

Reviewing files that changed from the base of the PR and between 9b4e656 and 199da7d.

📒 Files selected for processing (1)

• crates/fbuild-deploy/src/rp2040.rs

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📝 Walkthrough

Walkthrough

UF2 copy failures now use a dedicated formatter. Windows error 1392 receives guidance about the synthetic BOOTSEL FAT volume, avoiding repair or formatting, and using BOOTSEL or the managed picotool fallback. A unit test verifies the resulting message.

Changes

UF2 copy error handling

Layer / File(s)	Summary
Format and test UF2 copy failures crates/fbuild-deploy/src/rp2040.rs	UF2 copy errors are formatted through a helper with Windows error 1392 guidance, and a unit test verifies the synthetic volume and managed picotool fallback messaging.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• FastLED/fbuild#1041: Introduces the RP2040 UF2/BOOTSEL copy-based deployer that this error-handling change updates.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/rp2040-windows-volume-diagnostic

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