…eritance, command.execute.before hook

Merges changes from anomalyco#6478:
- Add parallel subtask execution via Promise.all()
- Fix model inheritance for subtasks with parent context restoration
- Add command.execute.before plugin hook for pre-execution logic
- Improve model resolution with proper fallback chain:
  command frontmatter > agent model > session model > default model
- Extend SubtaskPart schema with model, parentAgent, parentModel fields
- Update task tool to use ctx.extra.model for model override

Closes #225

…fixes (#229)

* fix(opencode): restore variant field in session prompt API

The variant field was accidentally removed during a cherry-pick that fixed
plugin commands. This restores variant support in PromptInput, CommandInput,
and the corresponding message/command handlers.

* refactor(opencode): extract CORS logic to dedicated module

Move CORS origin validation to cors.ts for better testability and add
support for *.shuv.ai domain alongside *.opencode.ai.

* feat(app): add server URL persistence and welcome screen for hosted environments

- Persist active server selection across sessions (server.v4 storage)
- Add WelcomeScreen for hosted environments when server connection fails
- Add connection state machine (connecting/ready/needs_config/error)
- Add hosted environment detection utilities

* feat(app): improve review pane with width constraints and empty state

- Add REVIEW_PANE constants for centralized width configuration
- Enforce max review pane width ratio (33% of viewport)
- Handle window resize to maintain width constraints
- Add empty state UI when no files to review

* refactor(app): reorder header buttons for better UX

- Move Theme/Font pickers before Review and Terminal toggles
- Add clarifying comments for button groups

* feat: merge upstream PR anomalyco#6478 - parallel subtasks, model inheritance, command.execute.before hook

Merges changes from anomalyco#6478:
- Add parallel subtask execution via Promise.all()
- Fix model inheritance for subtasks with parent context restoration
- Add command.execute.before plugin hook for pre-execution logic
- Improve model resolution with proper fallback chain:
  command frontmatter > agent model > session model > default model
- Extend SubtaskPart schema with model, parentAgent, parentModel fields
- Update task tool to use ctx.extra.model for model override

Closes #225

---------

Co-authored-by: shuv <shuv@shuv.dev>

…eritance, command.execute.before hook

Merges changes from anomalyco#6478:
- Add parallel subtask execution via Promise.all()
- Fix model inheritance for subtasks with parent context restoration
- Add command.execute.before plugin hook for pre-execution logic
- Improve model resolution with proper fallback chain:
  command frontmatter > agent model > session model > default model
- Extend SubtaskPart schema with model, parentAgent, parentModel fields
- Update task tool to use ctx.extra.model for model override

Closes #225