## Why

Planka is a self-hosted Kanban board application with a REST API, but there is no CLI tool to interact with it programmatically. AI agents and automated workflows need a simple, scriptable interface to manage cards, tasks, and comments without using the web UI. A single Go binary (`pcli`) provides a lightweight, dependency-free tool that can be dropped into any CI/CD pipeline or agent environment.

## What Changes

- New Go binary `pcli` providing a Cobra-based CLI to interact with the Planka API
- Nested command structure: `pcli <resource> <action> [args] [flags]`
- Authentication via bearer token from environment variables (`PLANKA_URL`, `PLANKA_TOKEN`) — no login flow, no on-disk token storage
- JSON output by default with consistent `{"data": ..., "error": null}` response envelope
- Optional `--format=table` for human-readable output
- Read-only access to projects and boards
- Full CRUD for cards, comments, task lists, tasks, and labels
- Card operations: move, duplicate, assign/unassign users, add/remove labels
- Board and card activity log (actions) — read-only
- `card list --board <id>` enriches responses with `listName` (resolved from list data)
- Lists treated as an implementation detail — not exposed as top-level commands

## Capabilities

### New Capabilities
- `api-client`: HTTP client layer for Planka API — base client with auth, request/response handling, and per-resource methods
- `cli-commands`: Cobra command tree — project, board, card, comment, task-list, task, label subcommands with flags and argument parsing
- `output-formatting`: Response envelope and format switching — JSON default, table option, consistent error handling
- `card-operations`: Card-specific composite operations — move (list + position), duplicate, assign/unassign members, add/remove labels, enriched board-level card listing

### Modified Capabilities
None — greenfield project.

## Impact

- **New repository structure**: `main.go`, `cmd/`, `client/`, `model/`, `output/` packages
- **Dependencies**: Go module `github.com/dcgsteve/pcli`, Cobra library, standard library HTTP client
- **External API**: Depends on Planka v2.0 API (OpenAPI 3.0 spec in `planka-api.json`)
- **Environment**: Requires `PLANKA_URL` and `PLANKA_TOKEN` environment variables at runtime