Add QtPass skills for OpenCode

[annejan]

Summary

Add an OpenCode skill file (.opencode/skills/qtpass-tests/SKILL.md) that encodes:

• Project conventions (qmake, Qt Test framework)
• Test patterns (set+get, Windows guards, gitleaks avoidance)
• Build/run commands
• Guide for adding new test suites

Why this matters

Future agents can load this skill via the skill tool to quickly understand how to add tests for QtPass without needing to learn the conventions from scratch.

Testing

• Skill file follows OpenCode SKILL.md format
• YAML frontmatter validated

[coveralls]

coverage: 15.389%. remained the same
when pulling 3280ae5 on qtpass-test-skill
into 3a96b80 on main.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 19.26%. Comparing base (3a96b80) to head (3280ae5).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #758   +/-   ##
=======================================
  Coverage   19.26%   19.26%           
=======================================
  Files          38       38           
  Lines        2953     2953           
=======================================
  Hits          569      569           
  Misses       2384     2384           

Flag	Coverage Δ
qtpass	19.26% <ø> (ø)

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