feat: Kanban integration via Hermes dashboard plugin REST API

[ajianaz]

Problem

Corin has no way to view or interact with Hermes kanban boards. Hermes dashboard plugin exposes a full REST API (41 endpoints) at /api/plugins/kanban/ — this can be consumed by Corin without direct SQLite access.

Scope

Phase 1: Read-only Board View

• kanban_client.rs — reqwest client for Hermes dashboard API
• Health check: detect hermes dashboard availability on startup
• Tauri commands: kanban_board, kanban_task_detail, kanban_stats
• Svelte components: KanbanView.svelte, KanbanCard.svelte, KanbanDrawer.svelte
• Sidebar nav item for Kanban

Phase 2: Write Operations

• Create/update/assign/comment via HTTP
• Drag-and-drop column transitions

Phase 3: Live Updates

• WebSocket /events for real-time task changes
• Auto-refresh board on events

Architecture

Corin → reqwest → http://127.0.0.1:9119/api/plugins/kanban/*
                   → hermes dashboard plugin_api.py
                       → kanban.db (SQLite, WAL)

Key Details

• Auth: session bearer token from hermes dashboard
• Zero new Rust deps (reqwest already in Cargo.toml)
• Reference: Uteke doc corin-kanban-integration-api (namespace: codecora)

Acceptance Criteria

• Board view renders all columns (triage → done)
• Task cards show assignee, priority, age
• Task drawer shows detail + comments + events
• Board selector works (switch between boards)
• Graceful fallback when dashboard not running

Related

• Kanban task: t_99a0c2d4
• Existing issue: feat: Document engine — CodeMirror + uteke doc integration #73 (Document engine — will add kanban as separate concern)