feat: add multi-account support for providers

[shkumbinhasani]

Summary

Allow users to connect multiple accounts for the same provider (e.g., two OpenAI accounts or two GitHub Copilot accounts with different credentials).

Changes

• Add label field to auth schema for account identification
• Store aliased accounts with keys like openai:Work
• Aliased providers inherit models from base provider
• Fix SDK caching to use separate instances per provider ID
• Add UI flow for "Add another account" when provider is already connected
• Pass label through OAuth and API auth flows

How it works

1. User presses p to connect a provider
2. If provider is already connected, shows account management submenu
3. "Add another account" prompts for a label (e.g., "Work", "Personal")
4. Auth is stored under aliased key (e.g., github-copilot:Work)
5. Provider appears in model selector as "GitHub Copilot (Work)"
6. Each account has its own credentials but inherits models from base provider

Files changed

• packages/opencode/src/auth/index.ts - Added label field and helper functions
• packages/opencode/src/provider/provider.ts - Aliased provider loading + SDK cache fix
• packages/opencode/src/provider/auth.ts - Label support in OAuth flow
• packages/opencode/src/provider/models.ts - Schema updates
• packages/opencode/src/server/routes/provider.ts - API label parameter
• packages/opencode/src/cli/cmd/tui/component/dialog-provider.tsx - UI for managing accounts
• packages/sdk/js/src/v2/gen/* - Regenerated SDK types

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate PRs Found:

1. feat(auth): OAuth Marathon - multi-account credential rotation (feat(auth): OAuth Marathon - multi-account credential rotation #8590)

   • feat(auth): OAuth Marathon - multi-account credential rotation #8590
   • Likely related: Addresses multi-account support and credential rotation for providers, overlapping with the label field and account management features in PR feat: add multi-account support for providers #9827

2. feat: Multi-Account OAuth Rotation with Settings UI and CLI Enhancements (feat: Multi-Account OAuth Rotation with Settings UI and CLI Enhancements #9069)

   • feat: Multi-Account OAuth Rotation with Settings UI and CLI Enhancements #9069
   • Likely related: Directly addresses multi-account OAuth with UI and CLI enhancements, which aligns with the account management submenu and UI flow described in PR feat: add multi-account support for providers #9827

Both of these PRs appear to address similar multi-account functionality. You should review them to ensure PR #9827 doesn't duplicate existing work or if there are complementary aspects that should be coordinated.