Make AgentPreview tasks configuration-cache compatible

[static-var]

Summary

• remove execution-time Task.project access from listComposePreviews and captureComposePreviews
• move project-derived values into task inputs/properties
• pass renderer/support classpaths through Gradle task classpath inputs
• preserve fake/real rendering, PreviewParameter expansion, filters, viewport filters, and Android/CMP/KMP wiring
• add configuration-cache functional coverage that verifies cache storage and reuse

Verification

• build-brief ./gradlew spotlessCheck detekt :plugin:test :preview-scanner:test
• ANDROID_HOME=$HOME/Library/Android/sdk build-brief ./gradlew -p samples/android-compose-app :app:captureComposePreviews --configuration-cache
• repeated Android sample capture and verified configuration cache reuse
• ANDROID_HOME=$HOME/Library/Android/sdk build-brief ./gradlew -p samples/cmp-compose-app :composeApp:captureComposePreviews --configuration-cache
• repeated CMP sample capture and verified configuration cache reuse

VLR verification

In /Users/staticvar/Projects/vlr-gg:

ANDROID_HOME=$HOME/Library/Android/sdk build-brief --mode raw ./gradlew --configuration-cache :designsystem:captureComposePreviews -PagentPreview.previewNameFilter=PrismButtonPreview -PagentPreview.maxPreviewParameterValues=1 -PagentPreview.viewportFilter=phone --console=plain

Repeated the same command and verified configuration cache reuse.

Review

• Implementation delegated to subagent
• Review subagent requested identical-invocation reuse assertions
• Fix delegated to subagent
• Re-review approved with no findings