fix(quota): handle MiniMax M3/Token Plan API changes (#1589)

Extract shared MiniMax provider logic into minimax-shared.js factory
module used by both minimax-coding-plan and minimax-cn-coding-plan
as thin wrappers.

Endpoint fallback:
- Try /v1/token_plan/remains (M3/Token Plan) first
- Fall back to legacy /v1/api/openplatform/coding_plan/remains
- fetchEndpoint wrapped in try/catch so network/parse errors
  return null instead of throwing, ensuring fallback always runs

Model selection (pickChatModel):
- Prefer MiniMax-M* entries with non-zero total_count (Token Plan M3)
- Fall back to general/chat/text model names (legacy Coding Plan)
- Fall back to any entry with current_interval_remaining_percent
- Ultimate fallback to model_remains[0]

Usage calculation:
- token_plan endpoint: usage_count = remaining, so used = total - remaining
- coding_plan endpoint: usage_count = consumed (legacy behavior)
- Prefer current_interval_remaining_percent when count fields are zero
  (legacy Coding Plan accounts with percentage-based quotas)
- remains_time used as fallback for window duration (in milliseconds,
  confirmed via live API: 9664502ms = 2.68h in 5h window)

Window status:
- Respect current_weekly_status field: status 3 means the window is
  not applicable for the current plan tier (e.g. legacy plans without
  weekly limits). These windows are omitted from the result.
- Default to active when status field is absent (backward compatible).

Fixes #759 (percentage showing empty/null for legacy Coding Plan
accounts and incorrect percentages for M3/Token Plan accounts).

packages/web/server/lib/quota/DOCUMENTATION.md

@@ -28,8 +28,8 @@ These provider IDs are currently dispatchable via `fetchQuotaForProvider(provide
 | `openrouter` | OpenRouter | `providers/openrouter.js` | `openrouter` |
 | `zai-coding-plan` | z.ai | `providers/zai.js` | `zai-coding-plan`, `zai`, `z.ai` |
 | `zhipuai-coding-plan` | Zhipu AI Coding Plan | `providers/zhipuai-coding-plan.js` | `zhipuai-coding-plan`, `zhipuai`, `zhipu` |
-| `minimax-coding-plan` | MiniMax Coding Plan (minimax.io) | `providers/minimax-coding-plan.js` | `minimax-coding-plan` |
-| `minimax-cn-coding-plan` | MiniMax Coding Plan (minimaxi.com) | `providers/minimax-cn-coding-plan.js` | `minimax-cn-coding-plan` |
+| `minimax-coding-plan` | MiniMax Coding Plan (minimax.io) | `providers/minimax-coding-plan.js` / `providers/minimax-shared.js` | `minimax-coding-plan` |
+| `minimax-cn-coding-plan` | MiniMax Coding Plan (minimaxi.com) | `providers/minimax-cn-coding-plan.js` / `providers/minimax-shared.js` | `minimax-cn-coding-plan` |
 | `ollama-cloud` | Ollama Cloud | `providers/ollama-cloud.js` | Cookie file at `~/.config/ollama-quota/cookie` (raw session cookie string) |
 | `wafer` | Wafer.ai | `providers/wafer.js` | `wafer`, `wafer-ai`, `wafer_ai`, `wafer.ai` |
 
@@ -53,6 +53,16 @@ All providers should return results via shared helpers to preserve API shape:
 6. Update this file with the new provider ID, module path, and alias/auth details.
 7. Validate with `bun run type-check`, `bun run lint`, and `bun run build`.
 
+## MiniMax M3 / Token Plan migration
+
+In 2025/2026 MiniMax rebranded "Coding Plan" to "Token Plan" alongside the M3 model release. The API underwent breaking changes:
+
+- **Endpoint fallback**: The provider tries `/v1/token_plan/remains` (M3) first, falling back to legacy `/v1/api/openplatform/coding_plan/remains`.
+- **Field semantics**: On the `token_plan/remains` endpoint, `current_interval_usage_count` returns **remaining** quota (not consumed). The provider computes `used = total - remaining` for this endpoint. The legacy `coding_plan/remains` endpoint retains the old semantics (`usage_count = consumed`).
+- **Percentage-based plans**: Legacy Coding Plan accounts return `current_interval_total_count: 0` but include `current_interval_remaining_percent`. The provider prefers this field when count fields are absent.
+- **model_remains array**: Now contains entries for multiple model categories (chat, speech, video, image). The provider selects the chat-model entry by matching `MiniMax-M*`, then `general`/`chat`/`text` by name, then any entry with a remaining percent.
+- **Window status**: The `current_interval_status` and `current_weekly_status` fields indicate whether a window is active. Status `3` means the window is not applicable for the current plan tier (e.g. legacy plans without weekly limits). The provider omits inactive windows.
+
 ## Notes for contributors
 - Keep provider IDs stable; clients use them directly.
 - Avoid adding alias-based dispatch in `fetchQuotaForProvider`; dispatch currently expects exact provider IDs.