feat: add tri-state sidebar filters for File Types, Workspace, Dataset

Convert SearchSidebar.js to SearchSidebar.tsx with TypeScript types
and chip-driven filters. The sidebar now reads the q (search query)
from Redux and routes three filter keys to new components:

- mimeType → FileTypeSidebarFilter: maps ES aggregation MIME
  buckets to FILE_TYPE_CATEGORIES using mimeToCategory(), shows
  category-level tri-state checkboxes (off→include→exclude→off),
  with expandable sub-items showing individual MIME counts.

- workspace → TriStateSidebarSection: generic tri-state section
  that reads/writes workspace chips via setWorkspacesInQ.

- ingestion → TriStateSidebarSection: reads/writes dataset chips
  via setDatasetsInQ.

All other filter keys continue to use the existing SearchFilter
component unchanged. The updateSelectedFilters callback now strips
workspace/ingestion from legacy filter updates since those are now
chip-driven.

Both new components use the shared triStateCycle utility from PR2
for the off→positive→negative→off cycling logic, and the
TriStateCheckbox component for rendering.

Fix TriStateCheckbox import path for triStateCycle (was resolving
to wrong directory).

Add sidebar__mime-info SCSS class for indented MIME sub-items.
Add FileTypeSidebarFilter.spec.tsx with 14 tests covering
buildCategoryCounts, toggleCategory, getCategoryState, and
toggleCategoryExpanded.

Author: hoyla

frontend/src/js/components/SearchSidebar/FileTypeSidebarFilter.spec.tsx

@@ -0,0 +1,210 @@
+import React from "react";
+import FileTypeSidebarFilter, {
+  FileTypeSidebarFilterState,
+} from "./FileTypeSidebarFilter";
+import {
+  FILE_TYPE_CATEGORIES,
+  mimeToCategory,
+} from "../Search/fileTypeCategories";
+
+// ── helpers ──────────────────────────────────────────────────────────
+
+function buildAgg(
+  bucketsByPrefix: Record<string, { key: string; count: number }[]>,
+) {
+  return {
+    key: "mimeType",
+    buckets: Object.entries(bucketsByPrefix).map(([prefix, mimes]) => ({
+      key: prefix,
+      count: mimes.reduce((sum, m) => sum + m.count, 0),
+      buckets: mimes,
+    })),
+  };
+}
+
+function createInstance(
+  props: Partial<React.ComponentProps<typeof FileTypeSidebarFilter>> = {},
+) {
+  const defaults = {
+    positiveCategories: [] as string[],
+    negativeCategories: [] as string[],
+    onToggleCategory: jest.fn(),
+    agg: undefined,
+    isExpanded: true,
+    setExpanded: jest.fn(),
+  };
+  const merged = { ...defaults, ...props };
+  const inst = new FileTypeSidebarFilter(merged);
+  Object.defineProperty(inst, "props", { value: merged, writable: true });
+  inst.state = { expandedCategories: new Set() };
+  return inst;
+}
+
+// ── tests ────────────────────────────────────────────────────────────
+
+describe("FileTypeSidebarFilter", () => {
+  describe("buildCategoryCounts", () => {
+    test("returns empty maps when no agg", () => {
+      const inst = createInstance();
+      const { counts, mimeCounts, uncategorisedCount } =
+        inst.buildCategoryCounts();
+      expect(counts.size).toBe(0);
+      expect(mimeCounts.size).toBe(0);
+      expect(uncategorisedCount).toBe(0);
+    });
+
+    test("sums counts per category across prefixes", () => {
+      const agg = buildAgg({
+        "application/": [{ key: "application/vnd.ms-excel", count: 10 }],
+        "text/": [{ key: "text/csv", count: 5 }],
+      });
+      const inst = createInstance({ agg });
+      const { counts } = inst.buildCategoryCounts();
+      expect(counts.get("spreadsheet")).toBe(15);
+    });
+
+    test("tracks individual MIME counts", () => {
+      const agg = buildAgg({
+        "image/": [
+          { key: "image/jpeg", count: 20 },
+          { key: "image/png", count: 8 },
+        ],
+      });
+      const inst = createInstance({ agg });
+      const { mimeCounts } = inst.buildCategoryCounts();
+      expect(mimeCounts.get("image/jpeg")).toBe(20);
+      expect(mimeCounts.get("image/png")).toBe(8);
+    });
+
+    test("counts uncategorised MIMEs", () => {
+      const agg = buildAgg({
+        "application/": [
+          { key: "application/pdf", count: 5 },
+          { key: "application/x-custom-thing", count: 3 },
+          { key: "application/x-weird", count: 2 },
+        ],
+      });
+      const inst = createInstance({ agg });
+      const { counts, uncategorisedCount, uncategorisedMimes } =
+        inst.buildCategoryCounts();
+      expect(counts.get("pdf")).toBe(5);
+      expect(uncategorisedCount).toBe(5);
+      expect(uncategorisedMimes).toHaveLength(2);
+      expect(uncategorisedMimes[0]).toEqual({
+        key: "application/x-custom-thing",
+        count: 3,
+      });
+    });
+
+    test("all known MIMEs map to a category", () => {
+      FILE_TYPE_CATEGORIES.forEach((cat) => {
+        cat.mimes.forEach((mime) => {
+          expect(mimeToCategory(mime)).toBe(cat.value);
+        });
+      });
+    });
+  });
+
+  describe("toggleCategory (tri-state via triStateCycle)", () => {
+    test("off → positive: adds to positive", () => {
+      const onToggle = jest.fn();
+      const inst = createInstance({
+        positiveCategories: ["pdf"],
+        negativeCategories: [],
+        onToggleCategory: onToggle,
+      });
+      inst.toggleCategory("image", {
+        stopPropagation: jest.fn(),
+      } as unknown as React.MouseEvent);
+      expect(onToggle).toHaveBeenCalledWith({
+        positive: ["pdf", "image"],
+        negative: [],
+      });
+    });
+
+    test("positive → negative: moves from positive to negative", () => {
+      const onToggle = jest.fn();
+      const inst = createInstance({
+        positiveCategories: ["pdf", "image"],
+        negativeCategories: [],
+        onToggleCategory: onToggle,
+      });
+      inst.toggleCategory("pdf", {
+        stopPropagation: jest.fn(),
+      } as unknown as React.MouseEvent);
+      expect(onToggle).toHaveBeenCalledWith({
+        positive: ["image"],
+        negative: ["pdf"],
+      });
+    });
+
+    test("negative → off: removes from negative", () => {
+      const onToggle = jest.fn();
+      const inst = createInstance({
+        positiveCategories: [],
+        negativeCategories: ["pdf"],
+        onToggleCategory: onToggle,
+      });
+      inst.toggleCategory("pdf", {
+        stopPropagation: jest.fn(),
+      } as unknown as React.MouseEvent);
+      expect(onToggle).toHaveBeenCalledWith({
+        positive: [],
+        negative: [],
+      });
+    });
+
+    test("stopPropagation is called", () => {
+      const stopProp = jest.fn();
+      const inst = createInstance({ onToggleCategory: jest.fn() });
+      inst.toggleCategory("pdf", {
+        stopPropagation: stopProp,
+      } as unknown as React.MouseEvent);
+      expect(stopProp).toHaveBeenCalled();
+    });
+  });
+
+  describe("getCategoryState", () => {
+    test("returns 'positive' for positive categories", () => {
+      const inst = createInstance({ positiveCategories: ["pdf"] });
+      expect(inst.getCategoryState("pdf")).toBe("positive");
+    });
+
+    test("returns 'negative' for negative categories", () => {
+      const inst = createInstance({ negativeCategories: ["image"] });
+      expect(inst.getCategoryState("image")).toBe("negative");
+    });
+
+    test("returns 'off' for unselected categories", () => {
+      const inst = createInstance();
+      expect(inst.getCategoryState("pdf")).toBe("off");
+    });
+  });
+
+  describe("toggleCategoryExpanded", () => {
+    test("expands a collapsed category", () => {
+      const inst = createInstance();
+      let newState: FileTypeSidebarFilterState | undefined;
+      inst.setState = ((
+        fn: (prev: FileTypeSidebarFilterState) => FileTypeSidebarFilterState,
+      ) => {
+        newState = fn(inst.state);
+      }) as typeof inst.setState;
+      inst.toggleCategoryExpanded("pdf");
+      expect(newState!.expandedCategories.has("pdf")).toBe(true);
+    });
+
+    test("collapses an expanded category", () => {
+      const inst = createInstance();
+      inst.state.expandedCategories.add("pdf");
+      let newState: FileTypeSidebarFilterState | undefined;
+      inst.setState = ((
+        fn: (prev: FileTypeSidebarFilterState) => FileTypeSidebarFilterState,
+      ) => {
+        newState = fn(inst.state);
+      }) as typeof inst.setState;
+      inst.toggleCategoryExpanded("pdf");
+      expect(newState!.expandedCategories.has("pdf")).toBe(false);
+    });
+  });
+});