feat: all-live Playwright tests, result dialog fix, runs panel fix

- Rewrote workbench tests: ZERO mocks, all 8 tests use live LLM
- Fixed RunsSidePanel: min-height for layout, runs visible on load
- Fixed parseRunOutput: strips markdown fences from LLM output
- Fixed chart widgets: pie/bar handle non-numeric values, proper sizing
- Fixed dialog close: tests use X button (in viewport) not Close (scrolled)
- Total: 43 tests, all passing, all live (1.1 min)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: abossard

frontend/src/features/workbench/WorkbenchPage.jsx

@@ -37,7 +37,8 @@ const useStyles = makeStyles({
   agentsLayout: {
     display: 'flex',
     gap: tokens.spacingHorizontalL,
-    alignItems: 'flex-start',
+    alignItems: 'stretch',
+    minHeight: '500px',
   },
   agentsMain: {
     flex: 1,