fix(quickemu): remove integrated OpenCore support, require OpenCore.qcow2

[flexiondotorg]

• Remove integrated OpenCore creation/extraction code from quickget: require_mtools/sgdisk helpers, create_macos_disk_with_opencore, download_opencore and related logic
• Simplify quickemu macOS boot flow to expect a separate OpenCore.qcow2 or ESP.qcow2; streamline device/drive argument construction
• Remove mtools and gptfdisk from devshell.nix and package.nix
• Always download OpenCore.qcow2 via legacy method and update status messages

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Documentation (updates the documentation)

Checklist:

• I have performed a self-review of my code
• I have tested my code in common scenarios and confirmed there are no regressions
• I have made corresponding changes to the documentation (remove if no documentation changes were required)

[cubic-dev-ai]

1 issue found across 4 files

Confidence score: 4/5

• Small risk: the only issue is a low-severity (4/10) error-reporting bug that could mask a prior firmware error message.
• In quickemu, overwriting MAC_MISSING can hide an existing "Firmware" error when both firmware and bootloader are missing, which could mislead users during troubleshooting.
• Pay close attention to quickemu - preserve existing error state when setting MAC_MISSING.

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="quickemu">

<violation number="1" location="quickemu:924">
P2: This unconditionally overwrites `MAC_MISSING`, hiding a previous "Firmware" error. If both firmware and bootloader are missing, only "Bootloader" error is shown. Consider preserving existing errors:
```bash
[ -z "${MAC_MISSING}" ] && MAC_MISSING="Bootloader"
```</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

P2: This unconditionally overwrites MAC_MISSING, hiding a previous "Firmware" error. If both firmware and bootloader are missing, only "Bootloader" error is shown. Consider preserving existing errors:

[ -z "${MAC_MISSING}" ] && MAC_MISSING="Bootloader"

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At quickemu, line 924:

<comment>This unconditionally overwrites `MAC_MISSING`, hiding a previous "Firmware" error. If both firmware and bootloader are missing, only "Bootloader" error is shown. Consider preserving existing errors:
```bash
[ -z "${MAC_MISSING}" ] && MAC_MISSING="Bootloader"
```</comment>

<file context>
@@ -915,32 +915,21 @@ function configure_bios() {
-            # No separate bootloader file needed
-            MAC_BOOTLOADER=""
-            MAC_BOOT_MODE="integrated"
+            MAC_MISSING="Bootloader"
         fi
 
</file context>

Suggested change

	MAC_MISSING="Bootloader"
	[ -z "${MAC_MISSING}" ] && MAC_MISSING="Bootloader"