Icon asset generation on macOS < v26 throws misleading error "only supported on macOS"

[barremian]

Is your feature request related to a problem? Please describe.

Running wails3 generate icons -iconcomposerinput <icon-file> -macassetdir <output-folder> on macOS < v26 throws the misleading error message "mac asset generation is only supported on macOS"

Describe the solution you'd like

The error message thrown to the user specifies that macOS asset generation based on Icon Compose input file works only on macOS >= v26

Describe alternatives you've considered

No response

Additional context

 Wails (v3.0.0-alpha.74)  Wails Doctor

# System

┌─────────────────────────────────────────────────┐
| Name          | MacOS                           |
| Version       | 15.7.4                          |
| ID            | 24G517                          |
| Branding      | Sequoia                         |
| Platform      | darwin                          |
| Architecture  | arm64                           |
| Apple Silicon | true                            |
| CPU           | Apple M1                        |
| CPU 1         | Apple M1                        |
| CPU 2         | Apple M1                        |
| GPU           | 8 cores, Metal Support: Metal 3 |
| Memory        | 16 GB                           |
└─────────────────────────────────────────────────┘

# Build Environment

┌────────────────────────────────┐
| Wails CLI    | v3.0.0-alpha.74 |
| Go Version   | go1.25.7        |
| -buildmode   | exe             |
| -compiler    | gc              |
| CGO_CFLAGS   |                 |
| CGO_CPPFLAGS |                 |
| CGO_CXXFLAGS |                 |
| CGO_ENABLED  | 1               |
| CGO_LDFLAGS  |                 |
| GOARCH       | arm64           |
| GOARM64      | v8.0            |
| GOOS         | darwin          |
└────────────────────────────────┘

# Dependencies

┌──────────────────────────────────────────────────────────────────────────────┐
| npm             | 11.6.2                                                     |
| *NSIS           | v3.11                                                      |
| Xcode cli tools | 2410                                                       |
| docker          | *Docker version 28.5.2, build ecc6942 (daemon not running) |
|                                                                              |
└────────────────────────── * - Optional Dependency ───────────────────────────┘

# Checking for issues

 SUCCESS  No issues found

# Diagnosis

 SUCCESS  Your system is ready for Wails development!

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