Fix wrapped company issue prefix conflicts (#6423)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies.
> - Company creation is the first control-plane object operators create,
and the generated issue prefix becomes part of task identity.
> - The company service already retries when a generated issue prefix
collides with the `companies_issue_prefix_idx` unique constraint.
> - Drizzle 0.45.x wraps PostgreSQL errors in `DrizzleQueryError`,
leaving the real `23505` constraint error on the `.cause` chain.
> - The existing retry detector only inspected the top-level error, so
wrapped prefix collisions surfaced as 500s instead of retrying.
> - This pull request walks the error cause chain for the exact prefix
constraint and verifies the retry path against embedded Postgres.
> - The benefit is company creation no longer fails when generated
prefixes collide under Drizzle 0.45.x wrappers.

## What Changed

- Walk the error `.cause` chain when detecting
`companies_issue_prefix_idx` unique violations, with a cycle guard and
support for `constraint` / `constraint_name` fields.
- Added an embedded Postgres regression test that seeds `ARO`, creates
`Aron & Sharon`, and verifies the retry produces `AROA`.
- Stabilized existing async tests touched by full verification: instance
sidebar plugin rendering now waits for React Query results, and
Tailscale-unavailable CLI tests explicitly hide host `tailscale`
detection.

## Verification

- `pnpm --filter @paperclipai/server exec vitest run
src/__tests__/companies-service.test.ts`
- `pnpm --filter @paperclipai/server exec vitest run
src/__tests__/heartbeat-stale-queue-invalidation.test.ts`
- `pnpm --filter @paperclipai/ui exec vitest run
src/components/InstanceSidebar.test.tsx`
- `pnpm --filter paperclipai exec vitest run
src/__tests__/network-bind.test.ts src/__tests__/onboard.test.ts`
- `pnpm test:run`
- `pnpm -r typecheck`
- `pnpm build`

## Risks

- Low runtime risk: the retry behavior only expands detection for the
existing exact company issue-prefix unique constraint.
- The cause-chain walk is bounded by visited objects to avoid cycles.
- The sidebar and CLI changes are test-only stabilization and do not
change production behavior.

> 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 Codex, GPT-5 coding agent in Codex desktop, with local
shell/tool execution.

## 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, I have included before/after
screenshots (N/A: no UI behavior change)
- [x] I have updated relevant documentation to reflect my changes (N/A:
bug fix with no user-facing docs change)
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

Closes #6350

ui/src/components/InstanceSidebar.test.tsx

@@ -223,9 +223,14 @@ describe("InstanceSidebar", () => {
     await flushReact();
     await findPluginLinks(container, 1);
 
-    const topLevelLinks = Array.from(
-      container.querySelectorAll<HTMLAnchorElement>('a[href^="/instance/settings/"]'),
-    );
+    await vi.waitFor(() => {
+      const links = Array.from(
+        container.querySelectorAll<HTMLAnchorElement>('a[href^="/instance/settings/"]'),
+      );
+      expect(links.some((a) => a.getAttribute("href") === "/instance/settings/plugins/linear")).toBe(true);
+    });
+
+    const topLevelLinks = Array.from(container.querySelectorAll<HTMLAnchorElement>('a[href^="/instance/settings/"]'));
     const hrefs = topLevelLinks.map((a) => a.getAttribute("href"));
 
     const pluginsIndex = hrefs.indexOf("/instance/settings/plugins");
@@ -266,6 +271,9 @@ describe("InstanceSidebar", () => {
     queryClient = rendered.queryClient;
     await flushReact();
 
+    await vi.waitFor(() => {
+      expect(mockPluginsApi.list).toHaveBeenCalled();
+    });
     const pluginLinks = Array.from(container.querySelectorAll('a[href^="/instance/settings/plugins/"]'));
     expect(pluginLinks).toHaveLength(0);
   });