feat: display Anthropic and OpenAI OAuth usage in status dialog and sidebar

[phj1081]

Summary

Adds real-time usage display for Anthropic and OpenAI OAuth accounts in both the status dialog (/status) and the sidebar.

Features

• Anthropic Usage: Shows 5-hour and 7-day rate limit windows with utilization % and reset times
• OpenAI Usage: Shows primary/secondary rate limit windows, plan type (Free/Plus/Pro/etc), and credits balance
• Visual Progress Bars: Color-coded bars (green → yellow → red) based on utilization level
• Reset Time Display: Human-readable countdown (e.g., "2h 15m", "5d 3h")

Screenshots

Status Dialog (/status or Ctrl+X S)

Anthropic Usage
5h:  ██░░░░░░░░░░░░░░░░░░ 9%   (reset: 2h 15m)
7d:  ████░░░░░░░░░░░░░░░░ 21%  (reset: 5d 3h)

OpenAI Usage (Pro)
5h:  ░░░░░░░░░░░░░░░░░░░░ 0%   (reset: 4h 59m)
7d:  ██████░░░░░░░░░░░░░░ 30%  (reset: 4d 2h)
Credits: $1000.00

Sidebar (collapsible Usage section)

▼ Usage
Anthropic
5h █░░░░░░░░░ 9% (2h 15m)
7d ██░░░░░░░░ 21% (5d 3h)
OpenAI (Pro)
5h ░░░░░░░░░░ 0% (4h 59m)
7d ███░░░░░░░ 30% (4d 2h)

Implementation

New Files

• src/usage/anthropic.ts: Fetches from api.anthropic.com/api/oauth/usage
• src/usage/openai.ts: Fetches from chatgpt.com/backend-api/wham/usage

Modified Files

• dialog-status.tsx: Added usage sections with progress bars
• sidebar.tsx: Added collapsible Usage section

API Details

Provider	Endpoint	Auth
Anthropic	GET api.anthropic.com/api/oauth/usage	OAuth token + anthropic-beta: oauth-2025-04-20
OpenAI	GET chatgpt.com/backend-api/wham/usage	OAuth Bearer token

Related

• #6298 - Plan usage tracking (z.ai) - Similar feature for different provider. Could potentially be integrated with their registry pattern in the future.

Notes

• Only shows usage when OAuth is configured (falls back gracefully if not)
• Uses Zod for runtime validation of API responses
• Sidebar uses compact 10-char progress bar; status dialog uses 20-char bar