feat: add fuzzy filter to TUI session picker

Users can now type to filter sessions in real-time:
- FilterableSelectList component wraps pi-tui's fuzzyFilter
- Matches against displayName, label, subject, sessionId
- j/k navigation, Enter selects, Escape clears filter then cancels
- Uses derivedTitle from previous commit for better display

Refs #1161

src/tui/components/filterable-select-list.ts

@@ -0,0 +1,176 @@
+import {
+  Input,
+  type SelectItem,
+  SelectList,
+  type SelectListTheme,
+  fuzzyFilter,
+} from "@mariozechner/pi-tui";
+import type { Component } from "@mariozechner/pi-tui";
+import chalk from "chalk";
+
+export interface FilterableSelectItem extends SelectItem {
+  /** Additional searchable fields beyond label */
+  searchText?: string;
+}
+
+export interface FilterableSelectListTheme extends SelectListTheme {
+  filterLabel: (text: string) => string;
+  filterInput: (text: string) => string;
+}
+
+/**
+ * Combines text input filtering with a select list.
+ * User types to filter, arrows/j/k to navigate, Enter to select, Escape to clear/cancel.
+ */
+export class FilterableSelectList implements Component {
+  private input: Input;
+  private selectList: SelectList;
+  private allItems: FilterableSelectItem[];
+  private theme: FilterableSelectListTheme;
+  private filterText = "";
+
+  onSelect?: (item: SelectItem) => void;
+  onCancel?: () => void;
+
+  constructor(
+    items: FilterableSelectItem[],
+    maxVisible: number,
+    theme: FilterableSelectListTheme,
+  ) {
+    this.allItems = items;
+    this.theme = theme;
+
+    this.input = new Input();
+    this.selectList = new SelectList(items, maxVisible, theme);
+
+    // Wire up input to filter the list
+    this.input.onSubmit = () => {
+      const selected = this.selectList.getSelectedItem();
+      if (selected) {
+        this.onSelect?.(selected);
+      }
+    };
+
+    this.input.onEscape = () => {
+      if (this.filterText) {
+        // First escape clears filter
+        this.filterText = "";
+        this.input.setValue("");
+        this.selectList.setFilter("");
+        this.selectList.setSelectedIndex(0);
+      } else {
+        // Second escape cancels
+        this.onCancel?.();
+      }
+    };
+  }
+
+  private getSearchText(item: FilterableSelectItem): string {
+    const parts = [item.label];
+    if (item.description) parts.push(item.description);
+    if (item.searchText) parts.push(item.searchText);
+    return parts.join(" ");
+  }
+
+  private applyFilter(): void {
+    const query = this.filterText.toLowerCase().trim();
+    if (!query) {
+      // Reset to all items
+      this.selectList = new SelectList(
+        this.allItems,
+        this.selectList["maxVisible"],
+        this.theme,
+      );
+      this.selectList.onSelect = this.onSelect;
+      this.selectList.onCancel = this.onCancel;
+      return;
+    }
+
+    // Use fuzzy filter from pi-tui
+    const filtered = fuzzyFilter(this.allItems, query, (item) =>
+      this.getSearchText(item),
+    );
+
+    this.selectList = new SelectList(
+      filtered,
+      this.selectList["maxVisible"],
+      this.theme,
+    );
+    this.selectList.onSelect = this.onSelect;
+    this.selectList.onCancel = this.onCancel;
+  }
+
+  invalidate(): void {
+    this.input.invalidate();
+    this.selectList.invalidate();
+  }
+
+  render(width: number): string[] {
+    const lines: string[] = [];
+
+    // Filter input row
+    const filterLabel = this.theme.filterLabel("Filter: ");
+    const inputLines = this.input.render(width - 8);
+    const inputText = inputLines[0] ?? "";
+    lines.push(filterLabel + inputText);
+
+    // Separator
+    lines.push(chalk.dim("─".repeat(width)));
+
+    // Select list
+    const listLines = this.selectList.render(width);
+    lines.push(...listLines);
+
+    return lines;
+  }
+
+  handleInput(keyData: string): void {
+    // Navigation keys go to select list
+    if (keyData === "\x1b[A" || keyData === "\x1b[B" || keyData === "k" || keyData === "j") {
+      // Map vim keys to arrows for selectList
+      if (keyData === "k") keyData = "\x1b[A";
+      if (keyData === "j") keyData = "\x1b[B";
+      this.selectList.handleInput(keyData);
+      return;
+    }
+
+    // Enter selects
+    if (keyData === "\r" || keyData === "\n") {
+      const selected = this.selectList.getSelectedItem();
+      if (selected) {
+        this.onSelect?.(selected);
+      }
+      return;
+    }
+
+    // Escape: clear filter or cancel
+    if (keyData === "\x1b" || keyData === "\x1b\x1b") {
+      if (this.filterText) {
+        this.filterText = "";
+        this.input.setValue("");
+        this.applyFilter();
+      } else {
+        this.onCancel?.();
+      }
+      return;
+    }
+
+    // All other input goes to filter
+    const prevValue = this.input.getValue();
+    this.input.handleInput(keyData);
+    const newValue = this.input.getValue();
+
+    if (newValue !== prevValue) {
+      this.filterText = newValue;
+      this.applyFilter();
+    }
+  }
+
+  getSelectedItem(): SelectItem | null {
+    return this.selectList.getSelectedItem();
+  }
+
+  getFilterText(): string {
+    return this.filterText;
+  }
+}

src/tui/components/selectors.ts

@@ -1,5 +1,14 @@
 import { type SelectItem, SelectList, type SettingItem, SettingsList } from "@mariozechner/pi-tui";
-import { searchableSelectListTheme, selectListTheme, settingsListTheme } from "../theme/theme.js";
+import {
+  filterableSelectListTheme,
+  searchableSelectListTheme,
+  selectListTheme,
+  settingsListTheme,
+} from "../theme/theme.js";
+import {
+  FilterableSelectList,
+  type FilterableSelectItem,
+} from "./filterable-select-list.js";
 import { SearchableSelectList } from "./searchable-select-list.js";
 
 export function createSelectList(items: SelectItem[], maxVisible = 7) {
@@ -10,6 +19,10 @@ export function createSearchableSelectList(items: SelectItem[], maxVisible = 7)
   return new SearchableSelectList(items, maxVisible, searchableSelectListTheme);
 }
 
+export function createFilterableSelectList(items: FilterableSelectItem[], maxVisible = 7) {
+  return new FilterableSelectList(items, maxVisible, filterableSelectListTheme);
+}
+
 export function createSettingsList(
   items: SettingItem[],
   onChange: (id: string, value: string) => void,