Increase AI server test coverage

[roncodes]

Summary

This draft PR wires backend coverage reporting into the AI package CI and brings ./server backend coverage to 100%.

Coverage reporting was also fixed for class coverage. The summary no longer reports 0.00% classes when Clover omits aggregate coveredclasses; it derives class coverage from file-level metrics instead.

Current Coverage

Latest successful backend CI run: 29675093569

Metric	Current	Covered / Total
Line coverage	100.00%	1332 / 1332 statements
Method coverage	100.00%	152 / 152 methods
Class coverage	100.00%	23 / 23 classes

Latest Clover check reports no uncovered backend statements.

Coverage Added

• Added regression coverage for the class coverage summary calculation.
• Expanded backend Pest coverage across attachment resolution, task/session controllers, admin endpoints, query executor authorization paths, provider guards, usage labels, task apply/session flows, and task/provider error handling.
• Added protected query/helper seams where needed so tests can exercise backend branches without executing real database queries.
• Excluded only framework-bound adapter defaults from coverage: package-load guards, Eloquent static query/create adapters, Laravel Setting/Auth/DB facade adapters, and the isolated Anthropic test-error HTTP boundary. Their calling behavior is covered through injectable/overridable helpers.
• Fixed test formatting under the repository PHP CS Fixer rules so CI lint remains stable.

Validation

• composer lint
• php -l on touched backend source/test files
• git diff --check
• git diff --cached --check
• GitHub Actions backend build passed with coverage artifact
• GitHub Actions frontend build passed

Notes

Local composer test:unit remains blocked in this shell because Pest dependencies are not installed locally (Unable to find Pest. Run composer install first.). CI installs dependencies and is the authoritative backend test/coverage signal for this PR.