feat: add dialog API for plugins

[ShamanicArts]

Closes #9911

What does this PR do?

Plugins currently can't interact with users beyond tool outputs. This adds a dialog API letting plugins create native interactive dialogs (select, confirm, alert, prompt) with full keyboard support.

Changes

• packages/opencode/src/dialog/index.ts - Core dialog module
• packages/opencode/src/server/routes/dialog.ts - Dialog reply endpoint
• packages/opencode/src/plugin/index.ts - Exposes dialog.show() to plugins
• packages/plugin/src/index.ts - Plugin-side types and hooks
• packages/opencode/src/cli/cmd/tui/routes/session/index.tsx - UI handlers

Example plugin

dialog-test.ts

Screenshots

How did you verify your code works?

Ran the opencode tests against changes.
Built mock plugins that called the newly implemented dialog api & tested in build

[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:

Based on my search results, I found one potentially related PR:

Related PR:

• PR feat: add ask_user tool for interactive user questions #6681: "feat: add ask_user tool for interactive user questions" (feat: add ask_user tool for interactive user questions #6681)
  • This could be related as it also deals with interactive user input/dialogs, though it appears to be focused on a specific ask_user tool rather than a general dialog API for plugins.

The other results (PR #5117 about agent details dialog and PR #9301 about /usage command) appear to be unrelated to the core dialog API feature.

No exact duplicate PRs found for the dialog API feature itself.