feat(desktop): stabilize connection workspace state

Absorb the local workspace drift for connection session handling, database switching, inspector readability helpers, and the bounded add-key preview flow.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/desktop/src/lib/add-key-draft.ts

@@ -0,0 +1,67 @@
+import {
+  buildDemoStringPreview,
+  formatDemoDurationFromMillis,
+  type DemoWorkspaceKey,
+} from "./demo-workspace";
+
+export type AddKeyDraft = {
+  name: string;
+  value: string;
+  ttlMillis: string;
+};
+
+export type AddKeyDraftErrors = Partial<Record<"name" | "ttlMillis", string>>;
+
+export function validateAddKeyDraft(draft: AddKeyDraft): AddKeyDraftErrors {
+  const errors: AddKeyDraftErrors = {};
+
+  if (!draft.name.trim()) {
+    errors.name = "Redis key name must not be empty.";
+  }
+
+  const ttlValue = draft.ttlMillis.trim();
+  if (ttlValue) {
+    if (!/^\d+$/.test(ttlValue)) {
+      errors.ttlMillis = "TTL must be an integer number of milliseconds when provided.";
+    } else if (Number.parseInt(ttlValue, 10) <= 0) {
+      errors.ttlMillis = "TTL must be greater than zero when provided.";
+    }
+  }
+
+  return errors;
+}
+
+export function parseOptionalTtlMillis(value: string) {
+  const normalized = value.trim();
+  if (!normalized) {
+    return null;
+  }
+
+  const parsed = Number.parseInt(normalized, 10);
+  return Number.isFinite(parsed) ? parsed : null;
+}
+
+export function findDuplicateKeyName<T extends { name: string }>(
+  keys: T[],
+  keyName: string,
+) {
+  const normalized = keyName.trim();
+  return keys.some((key) => key.name === normalized);
+}
+
+export function createDemoKeyRecord(draft: AddKeyDraft): DemoWorkspaceKey {
+  const keyName = draft.name.trim();
+  const ttlMillis = parseOptionalTtlMillis(draft.ttlMillis);
+
+  return {
+    id: keyName,
+    name: keyName,
+    type: "string",
+    ttl: ttlMillis === null ? "persistent" : formatDemoDurationFromMillis(ttlMillis),
+    preview: buildDemoStringPreview(draft.value),
+    editable: true,
+    value: draft.value,
+    summary:
+      "String-only Add Key flow stays aligned to the bounded create contract and keeps the new key visible in the current workspace scope.",
+  };
+}