🤖 Implement /new workspace creation command

[ammar-agent]

Adds /new <workspace> [-t <trunk>] slash command for creating workspaces from chat input.

Changes

• New slash command: /new <workspace-name> [-t <branch>] creates workspace with optional trunk specification
• Centralized command handlers: Extracted command logic from ChatInput to src/utils/chatCommands.ts (~350 lines)
• Modal integration: NewWorkspaceModal displays equivalent command string for user education
• Shared creation logic: Both modal and command paths use same backend API

Implementation

Command Syntax

/new feature-x              # Auto-detect trunk
/new feature-x -t develop   # Specify trunk
/new feature-x\nStart here  # With initial message

Invalid syntax (unknown flags, extra args, no args) opens the modal for guidance.

Architecture

Created chatCommands.ts utility with:

• createNewWorkspace() - Workspace creation with optional start message
• handleNewCommand() - Type-safe command handler
• handleCompactCommand() - Refactored from inline code
• formatNewCommand() - Command string generation (shared by modal)

ChatInput simplified from ~110 lines of inline logic to clean handler calls.

Testing

All 65 slash command tests pass:

• 11 new tests for /new command variations
• No regressions in existing commands
• TypeScript type checking passes

Design Decisions

Anti-pattern avoided: No /new-help command type. Invalid input opens modal instead, providing better UX than text help.

Type safety: Used CommandHandlerContext interface and discriminated unions throughout.

DRY: Both modal and command share backend API - no logic duplication.

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