[BUG] Desktop context ring shows no monthly budget spend for Enterprise plan seats

**Description**

Clicking the context ring in the bottom-right corner of Claude Code Desktop opens a popover. On a personal Pro/Max account, this popover shows, inline, with no further navigation:

1. "Context window" (e.g. "125.5k / 1M (13%)")
2. A "Plan usage limits · " section with:
- 5-hour limit (%)
- Weekly · all models (% + reset time)
- Usage credits ($X of $Y)

On an Enterprise plan seat, the popover only shows the "Context window" line and a "See detailed breakdown" link. The actual usage data *does* exist — clicking through to Settings surfaces a "Your usage limits · Enterprise" view showing spend vs. the org's monthly limit (e.g. "$4,411.85 of $5,000.00 spent · 88% used · Resets Mon, Aug 31, 6:00 PM MDT") — but it takes several extra clicks to get there instead of appearing inline in the popover.

I believe this used to show inline for Enterprise seats (spend vs. monthly limit, right in the popover) and stopped at some point — I don't have an exact version/date for when it changed, just recollection that it worked before. Flagging as a possible regression rather than a feature that never existed, in case that's useful for tracking down when it broke.

This matches/relates to prior reports:
- #52838 (Enterprise usage bar support) — closed as not planned on 2026-05-29
- #45079 (Desktop Code tab: No context window usage display) — closed as not planned on 2026-06-05
- #82481 (Pull Enterprise Org Spend-Limit Data in Claude Code (CLI/statusLine)) — same gap, framed as a feature request
- #84443 (`/api/oauth/usage` returns null spend/extra_usage for Enterprise orgs with per-member monthly spend limits — no parity with claude.ai Usage UI) — likely the actual root cause: if the API the popover reads from returns null for Enterprise orgs, that would explain why the popover has nothing to show here even though Settings displays the same data via a different path

Both #52838 and #45079 were closed as "not planned," but the underlying gap is still present as of the version below, and other users report seeing the same thing.

**Environment**
- Claude Code version: 2.1.235
- Client: Desktop app (macOS)
- Plan: Enterprise (org-level monthly spend limit, not the 5-hour/weekly cadence Pro/Max use)

**Expected behavior**
Clicking the context ring shows an inline usage-limits section for Enterprise (spend vs. monthly limit, reset date), matching how Pro/Max show their limits inline, instead of requiring navigation to Settings.

**Actual behavior**
Only "Context window" and "See detailed breakdown" appear in the popover. The actual spend-vs-limit data only appears after clicking through to Settings → Usage limits.

**Screenshots**
- Pro account popover (inline): Context window + "Plan usage limits · Pro" (5-hour limit 0%, Weekly all models 11% resets Thu 6:00 PM, Usage credits $1.92 of $20.00)
- Enterprise account popover (inline): only Context window (101.4k / 1M (10%)) + "See detailed breakdown" — no limits shown
- Enterprise Settings → usage limits (after clicking through): "Your usage limits · Enterprise" — $4,411.85 of $5,000.00 spent · 88% used · Resets Mon, Aug 31, 6:00 PM MDT
- Hover tooltip on the context ring (Enterprise): shows only "Context 103.7k / 1M (10%)" plus model/effort (Sonnet 5, Medium) — no usage-limit info here either

Start by reproducing the context-ring popover on an Enterprise seat, then compare it with Settings → Usage limits and inspect the `/api/oauth/usage` path mentioned in #84443. Done means the popover shows Enterprise spend, monthly limit, percentage used, and reset date inline without requiring navigation to Settings.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.