fix: support reliable CH585 ISP flashing

[hitsmaxft]

Summary

Adds a CH585-specific ISP flow for the programming constraints observed on real CH585 hardware. The implementation temporarily clears CFG_DEBUG_EN and CFG_ROM_READ, keeps the required key/session across erase and PROGRAM, starts a new key phase for VERIFY, restores the exact entry configuration only after full verification, and then resets.

Changes

• isolate CH585 policy in src/ch585.rs
• preserve the established non-CH585 flash, packet, and reset paths
• enforce CH585 two-byte BootROM operation status
• retain one CH585 key session from configuration through erase and PROGRAM
• use a fresh key phase for VERIFY
• restore the exact pre-flash configuration only after successful full verification
• make CH585 Debug enable change only bit 4 and verify complete readback
• avoid reapplying USB configuration 1 when it is already active

Validation

• host unit tests: 13/13 pass on macOS arm64 through the repository Nix environment
• release build: pass
• exact fork hardware run on CH585M UID 98-5B-29-5A-04-DC-C5-91: pass
  • input image: 596 bytes, padded to 600 bytes with FF
  • full erase: pass
  • program: pass
  • full verify: pass
  • configuration restored byte-for-byte: ffffffffffffffffd73f0f45
  • BootROM reset: pass
  • post-reset WCH-Link attach identified CH585 and an authenticated Debug Module v2
• CH582 regression tests: pass; physical CH582 testing was intentionally not run

Scope

Generic response-status changes already covered by PR #110 are intentionally not duplicated here.

[hitsmaxft]

this PR is tested well. It is ready to be merged.