[Nextor 3] Modify ZAP_ALL to skip drives assigned to device-based drivers

[Konamiman]

"Backport" of #147

• The semantics change from "when the drive is assigned to a device-based driver" to "when the drive is assigned to a Nextor driver" since device-based is the only type of driver supported by Nextor 3.
• Also fixes a bug in the original implementation: UD_FLAGS was being checked instead of UD_DFLAGS, and DE was being used instead of HL.

Part of #164

[coderabbitai]

📝 Walkthrough

Walkthrough

A conditional guard was added to the zap_all_loop routine to skip zapping units controlled by Nextor drivers by testing the UF_DBD bit in UD_DFLAGS, preserving subsequent UD_TIME handling while making zap conditional.

Changes

Cohort / File(s)	Summary
Nextor Driver Guard source/kernel/bank2/val.mac	Inserted conditional logic in zap_all_loop that reads UD_DFLAGS, tests the UF_DBD flag, and branches to skip zapping for units marked as controlled by Nextor drivers. UD_TIME handling unchanged.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A little rabbit hops with care,
I peek at flags and stop the snare,
If Nextor holds a unit tight,
I skip the zap and set things right,
Hooray for safe and gentle light!

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: modifying ZAP_ALL to skip drives assigned to device-based drivers, with Nextor 3 context.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@source/kernel/bank2/val.mac`:
- Around line 2767-2773: The code incorrectly loads UD_DFLAGS into DE
(clobbering the unit descriptor) and then adds it to HL (which points into
UNIT_TAB); instead load the UD_DFLAGS offset into HL (not DE) and then add HL,DE
so DE still contains the unit descriptor address before testing the UF_DBD bit;
i.e. replace the instruction "ld de,UD_DFLAGS" with "ld hl,UD_DFLAGS" so the
subsequent "add hl,de" and "bit UF_DBD,(hl)" operate on the correct address and
DE is preserved for later code (references: UD_DFLAGS, UF_DBD, no_zap_unit).