fix(ci): correct desktop path filter scope

[BrianInAz]

Summary

Correct the CI Desktop path filter so mobile, documentation, and Beads-only changes do not activate Desktop jobs.

Root cause

The filter used desktop/** plus !desktop/src-tauri/** while dorny/paths-filter uses predicate-quantifier: some. Each rule is therefore independent, and the negative rule matches every file outside desktop/src-tauri.

TDD remediation

• Red: 3/3 new routing contracts failed on untouched main
• Green: 3/3 new routing contracts passed
• Existing file-size contracts: 6/6 passed
• All existing Detect Changed Paths contract commands passed
• Workflow YAML parsing, Biome, and diff checks passed
• No dependency changes

The replacement is one positive extglob: desktop/!(src-tauri)/**. Tauri paths remain covered by the existing desktop-rust filter and downstream job conditions.

Documentation

• CI Desktop path-filter remediation
• Beads: ios-buzz-59e.8

Promotion

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