refactor: long-tail type-aware sweep (T3.c) (#759)

* refactor: long-tail type-aware sweep (T3.c)

Cluster T3.c — 15 files, 24 errors cleared.

Rules fixed:
- no-useless-default-assignment: 6 → 0 (mcp-server.ts — Zod .default() makes destructuring defaults redundant)
- no-unnecessary-type-assertion: 1 → 0 (workspace-registry-model.ts — remove redundant ! on string[])
- no-unsafe-enum-comparison: 3 → 0 (use-push-token-registration.ts, use-image-attachment-picker.ts — use PermissionStatus enum values)
- no-redundant-type-constituents: 6 → 0 (workspace-setup.ts, tool-call-detail-state.ts, workspace-draft-agent-tab.tsx, stream.test.ts, desktop-settings-commands.ts — unknown | T → unknown)
- no-unnecessary-type-parameters: 4 → 0 (indexeddb-attachment-store.test.ts, use-archive-agent.ts, class-mocks.ts, agent-stream-coalescer.ts — narrow interface / remove unused generics)
- no-unnecessary-type-conversion: 4 → 0 (session-context.tsx — remove String() on already-string values; class-mocks.ts — remove String(prop) after symbol guard)
- no-implied-eval: 1 → 0 (agent-stream-coalescer.test.ts — narrow timer interface to function-only, eliminating string overload)

Deferred (need caller updates or extra files beyond 15-file cap):
- no-unnecessary-type-parameters: host.ts:onResized/onDragDropEvent, electron/events.ts (callers pass typed handlers; removing generic breaks contravariance without cast)
- no-base-to-string: ~21 errors, 18 files
- restrict-template-expressions: ~11 errors, 9 files
- await-thenable: ~7 errors, 4 files
- no-unnecessary-type-conversion: ~9 remaining errors, 9 files

* fix(server): restore MCP tool handler defaults that the linter mis-flagged

The `no-useless-default-assignment` rule fires because Zod's `.default()`
chain makes the TypeScript type non-optional, so the linter treats the
destructuring defaults as redundant. But the MCP framework invokes
handlers with raw (untransformed) params — Zod defaults are not applied
before the call. The destructuring defaults are the runtime safety net.

Reverts the three handler changes from T3.c:
- send_prompt: background = false, notifyOnFinish = false
- list_agents: includeArchived = false, sinceHours = 48, limit = 50
- get_terminal_lines: stripAnsi = true

The no-useless-default-assignment errors on these lines remain and are
deferred to a future cluster that addresses the MCP framework integration.

packages/app/src/attachments/web/indexeddb-attachment-store.test.ts

@@ -3,8 +3,8 @@ import { createIndexedDbAttachmentStore } from "./indexeddb-attachment-store";
 
 type Listener = () => void;
 
-class FakeRequest<T = unknown> {
-  result!: T;
+class FakeRequest {
+  result!: unknown;
   error: Error | null = null;
   private listeners = new Map<string, Listener[]>();
 
@@ -70,7 +70,7 @@ describe("indexeddb attachment store", () => {
           const store = new FakeObjectStore((record) => {
             storedRecord = record;
           });
-          const request = new FakeRequest<FakeDatabase>();
+          const request = new FakeRequest();
           request.result = new FakeDatabase(store);
           queueMicrotask(() => request.emit("success"));
           return request;