- Update LaunchEvaluationModal to handle optional config
- Update FunctionSelector to use getPrefix instead of getItemIcon
- Add null coalescing for functions and config at call sites
- Fix 404 handling to use AppProviders instead of RootErrorBoundaryLayout
- Revert models/route.tsx to use local QUANTILES constant

…ding

Based on React Router 7 official patterns and industry best practices:

1. **Use undefined over null for unavailable data**
   - Changed useAllFunctionConfigs() to return undefined instead of null
   - Updated FunctionSelector to handle undefined gracefully with disabled state

2. **Remove scattered null coercion (??  {})**
   - Removed all `functions ?? {}` patterns across components
   - Let components properly handle undefined state

3. **Remove anti-pattern: catching errors to return fake empty data**
   - Removed loader try/catch blocks that returned empty arrays/objects
   - Let infrastructure errors throw to layout error boundaries naturally
   - Removed fake degraded states that hid real errors from users

4. **Let errors flow to proper boundaries**
   - Layout error boundaries handle infrastructure failures
   - Dashboard uses <Await errorElement> for granular per-metric errors
   - Pages with promises use React.use() which throws to boundaries

Research sources:
- https://reactrouter.com/how-to/error-boundary
- https://reactrouter.com/en/main/components/await
- https://reactrouter.com/6.30.2/guides/deferred

Routes updated:
- workflow_evaluations/route.tsx
- evaluations/route.tsx
- datasets/route.tsx
- observability/episodes/route.tsx
- index.tsx (dashboard)

Replace use() hook with Await component pattern across all data-loading
components for inline error handling. This allows errors to be displayed
at the lowest possible UI level - tables show "Error loading data" while
page headers and navigation remain functional.

Components updated:
- InferencesTable: Shows inline error instead of blank page
- EpisodesTable: Shows inline error with message extraction
- EpisodeInferenceTable: Shows inline error in episode detail
- DatasetTable: Shows inline error in datasets list
- DatasetRowTable: Shows inline error for datapoints
- AutopilotSessionsTable: Shows inline error for sessions
- PageLayout counts: Shows "—" with tooltip on count load failure
- Episode detail pagination/feedback sections

Also:
- Remove fake data catches from inferences loader (.catch(() => 0))
- Fix BigInt comparison bug (numInferences === 0n vs Number())
- Distinguish client 404s (!error.data) from resource 404s

- Defer modelInferences and feedback data as promises in loader
- Add skeleton and error components for streamed sections
- Update BasicInfo to support both promise (server) and resolved (client) data
- Replace use() with Await in autopilot session for consistent error handling
- Fix bigint to number conversion for processing_time_ms

…page

Port the full variant response logic from InferenceDetailContent to restore
TryWithButton functionality that was broken during streaming refactor.

- Add variant inference fetcher with proper request handling
- Add VariantResponseModal with demonstration feedback support
- Track resolved model inferences for usage calculation in modal
- Use useCallback for handleFeedbackAdded to satisfy exhaustive-deps