Implement Project Management API for Multi-Project Sessions

[riatzukiza]

Summary

This feature implements a comprehensive project management API that allows a single instance of Opencode to run sessions for multiple projects and different worktrees per project.

Context

The current Opencode instance manages sessions for a single project directory. This spec defines a new API structure to support multiple projects with multiple worktrees each, providing proper isolation and management capabilities.

Note: Some aspects are partially covered by issue anomalyco#1877 which proposes root folder aggregation and cwd metadata for sessions.

Requirements

API Implementation

Implement the following REST API endpoints:

GET /project -> Project[]
POST /project/init -> Project

GET /project/:projectID/session -> Session[]
GET /project/:projectID/session/:sessionID -> Session
POST /project/:projectID/session -> Session
{
  id?: string
  parentID?: string
  directory: string
}
DELETE /project/:projectID/session/:sessionID
POST /project/:projectID/session/:sessionID/init
POST /project/:projectID/session/:sessionID/abort
POST /project/:projectID/session/:sessionID/share
DELETE /project/:projectID/session/:sessionID/share
POST /project/:projectID/session/:sessionID/compact

GET /project/:projectID/session/:sessionID/message -> { info: Message, parts: Part[] }[]
GET /project/:projectID/session/:sessionID/message/:messageID -> { info: Message, parts: Part[] }
POST /project/:projectID/session/:sessionID/message -> { info: Message, parts: Part[] }

POST /project/:projectID/session/:sessionID/revert -> Session
POST /project/:projectID/session/:sessionID/unrevert -> Session
POST /project/:projectID/session/:sessionID/permission/:permissionID -> Session

GET /project/:projectID/session/:sessionID/find/file -> string[]
GET /project/:projectID/session/:sessionID/file -> { type: "raw" | "patch", content: string }
GET /project/:projectID/session/:sessionID/file/status -> File[]

POST /log

// Provider and config endpoints with directory resolution
GET /provider?directory=<resolve path> -> Provider
GET /config?directory=<resolve path> -> Config
GET /project/:projectID/agent?directory=<resolve path> -> Agent
GET /project/:projectID/find/file?directory=<resolve path> -> File

Key Features

1. Project Isolation: Each project maintains its own session namespace and configuration
2. Worktree Support: Sessions can be created for different working directories within a project
3. Session Management: Full CRUD operations for sessions within each project context
4. File Operations: File access and status operations scoped to project/session contexts
5. Directory Resolution: Provider, config, and agent endpoints support directory-based resolution

Definition of Done

• All API endpoints implemented with proper request/response validation
• Project and session data models implemented with appropriate persistence layer
• Directory resolution logic handles cross-project path references correctly
• Session isolation between projects is maintained
• Integration with existing Opencode CLI and TUI interfaces
• Comprehensive test coverage for all endpoints and edge cases
• Documentation for API usage and migration from single-project setup

Related Issues

• Partial overlap with Support a root folder for aggregating sessions across subdirectories in Opencode anomalyco/opencode#1877 (root folder aggregation and cwd metadata)