refactor(platform): phase 7/9 migrate serial, USB, and device mechanics

[zackees]

Parent: #1306
Depends on: phase 6 daemon IPC/lifecycle migration

Scope

Move host device mechanics behind fbuild_core::platform::device:

• serial-port enumeration/classification host seams;
• Windows PnP/SetupAPI and recovery primitives;
• Linux sysfs and macOS device facts;
• USB/removable-volume/topology primitives shared by serial and deployment;
• host-specific retry constants only when they are mechanics rather than product policy.

Preserve the FastLED/boards VID/PID source-of-truth rule and the existing Windows USB-CDC, DTR/RTS, recovery, and serial client contracts. Delete exact migrated ledger rows.

Acceptance criteria

• RED characterization covers representative Windows, Linux, and macOS device behavior.
• Shared serial/deploy callers leak no Win32, sysfs/IOKit, raw device, or concrete platform type.
• No production VID/PID data is added outside the published boards registry.
• Existing port probing, USB recovery, deploy preemption, and Python SerialMonitor behavior remains compatible.
• Before/after ledger totals and RED -> GREEN evidence are recorded.
• Focused serial/device tests, hardware-gated tests where required, three-host CI, workspace check/clippy, and repo tests are GREEN.