feat(studio): adopt shared Button actions

[gcomneno]

Closes #220

Summary

• upgrade the immutable giadaware-ui-components vendor to source commit 8a5144c;
• adopt the shared Studio Button component across 36 standard Studio actions;
• preserve native buttons only for specialized reorder and relation-search controls;
• replace global descendant button styling with public Giada UI button tokens;
• remove obsolete local button CSS;
• add a structural adoption contract covering imports, native-control allowlists, and legacy CSS removal;
• update upgrade, readiness, integration, and shutdown typing contracts.

Verification

• npm run check
• npm test — 329 tests passed
• npm run build
• focused Button, vendor, readiness, upgrade, and shutdown tests