GUI: Clarify qualifier asset validation

[Tabakkui]

Problem

The qualifier asset creation dialog reports only a generic invalid-character message. It does not tell the user that a qualifier must start with # and have at least three characters after the prefix. On narrow windows the long message also stays on one line and is clipped.

Approach

• Clarify the validation message with the required prefix, minimum length, and allowed characters.
• Enable word wrapping for the shared creation-dialog validation label.
• Add a focused asset validation regression assertion for the required guidance.

Test plan

• git diff --check
• XML/static regression assertions for the validation text and messageLabel.wordWrap
• Full C++ unit/build test not run on the ARM64 Pi; requires the authorized PC build environment.

Fixes #1046