Server-side pagination for large result sets

- ResultStore: execute query, store batches server-side, serve pages on demand
- POST /query/paged → returns query_id + total_rows + page count (no rows)
- GET /query/page/{id}/{page}?size=100 → returns one page of rows
- RecordBatch slicing for efficient page extraction from Arrow batches
- LRU eviction: keeps 50 most recent query results in memory
- Tested: 100K rows → 1,000 pages of 100, any page fetchable by number
- Supervisor pattern: chunk results, serve on demand, retry-safe (idempotent GET)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/ui/src/main.rs

@@ -1003,8 +1003,8 @@ fn ResultsTable(response: QueryResponse) -> Element {
         if response.row_count == 0 {
             div { class: "empty-sm", "no rows returned" }
         } else if let Some(rows) = rows {
-            if rows.len() > 200 {
-                div { class: "results-info", "Showing first 200 of {response.row_count} rows" }
+            if rows.len() > 500 {
+                div { class: "results-info", "Showing first 500 of {response.row_count} rows (use SQL tab with LIMIT for larger)" }
             }
             div { class: "table-wrap",
                 table {
@@ -1016,7 +1016,7 @@ fn ResultsTable(response: QueryResponse) -> Element {
                         }
                     }
                     tbody {
-                        for row in rows.iter().take(200) {
+                        for row in rows.iter().take(500) {
                             tr {
                                 for col in response.columns.iter() {
                                     td { {format_cell(row.get(&col.name))} }