improvement(ui): reuse collapsible cards for MCP tools
MCP tools now use the existing CollapsibleCard header and body instead of a restyled Button inside a local card. A new disabled prop blocks header activation and tab focus for tools without parameters while leaving independent card actions available.
Tool descriptions, issue tooltips, required/type badges and controlled expansion are preserved. Long tool names use OverflowText, and parameter content remains lazy while collapsed. The shared card uses 4px corners, its standard header/body spacing and fill, and a trailing badge slot. Disabled informational headers remain readable without opacity fading.
Validation: workspace type/import/API/lint checks, complete EMCN suite and 50consumer tests. Before/after screenshots use actual product rendering loops with local data; pointer/keyboard expansion, disabled controls and narrow/enlarged text were checked. No live MCP requests or captured issue-tooltip popup.
External full audit: 772→766 findings; all six targeted overrides removed with no new findings. Diff checker clean against the actual base.