[codex] Add local Cloud Upstream sync (#6548)

## Thinking Path

> - Paperclip is the control plane for AI-agent companies.
> - Operators need a path to move local company state toward Paperclip
Cloud without losing local-first control.
> - The Cloud Upstream flow needs API, persistence, CLI, and board UI
surfaces that agree on the same manifest/run model.
> - The existing branch had the feature work plus UX and error-handling
follow-ups.
> - This pull request packages the remaining Cloud Upstream sync work
into one standalone branch.
> - The benefit is an inspectable local-to-cloud sync workflow with
preview, conflicts, activation, and captured UX review states.

## What Changed

- Added Cloud Upstream shared types, server routes/services, and
persisted run schema/migration.
- Added Paperclip Cloud CLI sync helpers and local connection storage.
- Added the Cloud Upstream board UI, settings entry points, query keys,
and UX lab page.
- Added preview/activation checklist behavior, redirect handling,
manifest-only preview support, friendly errors, in-flight hints, and
entity count summaries.

## Verification

- `pnpm --filter @paperclipai/plugin-sdk build`
- `NODE_ENV=test pnpm exec vitest run cli/src/__tests__/cloud.test.ts
server/src/__tests__/instance-settings-routes.test.ts
server/src/__tests__/instance-settings-service.test.ts
ui/src/pages/CloudUpstream.test.tsx
ui/src/components/CompanySettingsSidebar.test.tsx`
- `NODE_ENV=test pnpm exec vitest run
server/src/__tests__/cloud-upstreams.test.ts`

Worktree setup note: the isolated worktree install skipped native sqlite
build scripts, so I copied the already-built local sqlite binding from
the main checkout before running
`server/src/__tests__/cloud-upstreams.test.ts`. The test then passed.

## Risks

- Medium: this adds a database migration and a broad feature path across
CLI/server/UI.
- Merge order: this is the only PR in this split with a DB migration;
merge it before any future Cloud Upstream migration follow-up.
- Mitigation: the PR is based directly on current `origin/master`, has
targeted route/service/UI tests, and keeps the feature behind existing
experimental Cloud Sync settings.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI GPT-5 Codex via `codex_local`, tool-enabled coding session;
exact context window not exposed by this runtime.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, screenshot artifacts are
intentionally omitted per reviewer request
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

ui/src/pages/InstanceExperimentalSettings.tsx

@@ -205,6 +205,7 @@ export function InstanceExperimentalSettings() {
 
   const enableEnvironments = experimentalQuery.data?.enableEnvironments === true;
   const enableIsolatedWorkspaces = experimentalQuery.data?.enableIsolatedWorkspaces === true;
+  const enableCloudSync = experimentalQuery.data?.enableCloudSync === true;
   const autoRestartDevServerWhenIdle = experimentalQuery.data?.autoRestartDevServerWhenIdle === true;
   const enableIssueGraphLivenessAutoRecovery =
     experimentalQuery.data?.enableIssueGraphLivenessAutoRecovery === true;
@@ -298,6 +299,24 @@ export function InstanceExperimentalSettings() {
         </div>
       </section>
 
+      <section className="rounded-xl border border-border bg-card p-5">
+        <div className="flex items-start justify-between gap-4">
+          <div className="space-y-1.5">
+            <h2 className="text-sm font-semibold">Cloud Sync</h2>
+            <p className="max-w-2xl text-sm text-muted-foreground">
+              Show local Paperclip Cloud upstream connection, preview, push, retry, and activation review surfaces.
+              Saved connections and run history are preserved when this is disabled.
+            </p>
+          </div>
+          <ToggleSwitch
+            checked={enableCloudSync}
+            onCheckedChange={() => toggleMutation.mutate({ enableCloudSync: !enableCloudSync })}
+            disabled={toggleMutation.isPending}
+            aria-label="Toggle cloud sync experimental setting"
+          />
+        </div>
+      </section>
+
       <section className="rounded-xl border border-border bg-card p-5">
         <div className="flex items-start justify-between gap-4">
           <div className="space-y-1.5">