feat(policies): backend-driven policy enforcement (frontend) (#6598)

## Summary
Adds the **Policies** feature (proprietary, behind the
`POLICIES_ENABLED` flag): backend-driven enforcement that runs a fixed
tool pipeline on documents, docked in the right tool sidebar alongside
Tools.

## Highlights
- **Policy catalog** — 5 categories; **Security** is wired (redact PII +
sanitize), the others are marked "Coming soon".
- **Backend as source of truth** — policies persist via the Policies
engine (`/api/v1/policies`), one policy per category, with a local cache
+ offline fallback.
- **Auto-run** — enabled policies run on every uploaded file: dispatch →
poll → import outputs into the workspace.
- **Security redact config** — PII preset dropdown + custom word/regex
entry + advanced options; tool params map to the backend endpoint
fields.
- **Activity feed** with retry on failures; **file badges** showing
which policies ran on a file (sidebar + files page), tinted to the
policy colour.
- Reuses the **Watched Folders** engine for each policy's backing
folder; policy-owned folders are filtered out of the Watched Folders UI.

## Notes
- Gated by `POLICIES_ENABLED` (true in proprietary, false in core) —
unreachable in the open-source build.
- Frontend-only diff; depends on the backend Policies engine and the
merged Watched Folders feature.

frontend/editor/src/proprietary/data/policyDefinitions.test.ts

@@ -0,0 +1,23 @@
+import { describe, it, expect } from "vitest";
+import { POLICY_CATEGORIES, POLICY_CONFIG } from "@app/data/policyDefinitions";
+
+describe("policy definitions integrity", () => {
+  it("every category has a matching config entry", () => {
+    for (const cat of POLICY_CATEGORIES) {
+      expect(POLICY_CONFIG[cat.id], `config for ${cat.id}`).toBeDefined();
+      expect(POLICY_CONFIG[cat.id].fields.length).toBeGreaterThan(0);
+      expect(POLICY_CONFIG[cat.id].rules.length).toBeGreaterThan(0);
+      // Every preset seeds a real, non-empty pipeline (the category→steps map).
+      expect(
+        POLICY_CONFIG[cat.id].defaultOperations.length,
+        `defaultOperations for ${cat.id}`,
+      ).toBeGreaterThan(0);
+    }
+  });
+  it("field keys are unique within each category", () => {
+    for (const cat of POLICY_CATEGORIES) {
+      const keys = POLICY_CONFIG[cat.id].fields.map((f) => f.key);
+      expect(new Set(keys).size).toBe(keys.length);
+    }
+  });
+});