docs(kanban): backfill multi-board refs in reference docs (#19704)

Followup to #19653. The feature PR updated the Kanban user guide but
missed four other pages that document the same surface. Caught when
Teknium asked 'did you add docs to the guide and any other kanban
related docs around this?'.

- reference/cli-commands.md: rewrite the `hermes kanban` section to
  document the `--board <slug>` global flag, the `boards`
  subcommand group (list/create/switch/show/rename/rm), board
  resolution order, and worked examples. Also fills in the
  `create` / `complete` flag lists that had drifted from the
  current CLI (`--summary`, `--metadata`, `--triage`,
  `--idempotency-key`, `--max-runtime`, `--skill`).
- reference/environment-variables.md: add `HERMES_KANBAN_BOARD`
  row, update `HERMES_KANBAN_DB` precedence note.
- reference/slash-commands.md: add `/kanban boards ...` and
  `/kanban --board <slug> ...` to the two `/kanban` rows (CLI
  table + gateway table).
- features/kanban-tutorial.md: the walkthrough uses the `default`
  board, so just a note pointing readers at the overview's Boards
  section if they want multiple queues, plus the corrected per-board
  DB path.

Skill docs (devops-kanban-orchestrator, -worker) intentionally not
updated: those are agent-facing lifecycle playbooks and boards are
transparent to workers (HERMES_KANBAN_BOARD env var pins the DB
automatically), so there's nothing new for a worker to know.

website/docs/reference/cli-commands.md

@@ -340,34 +340,64 @@ hermes cron <list|create|edit|pause|resume|run|remove|status|tick>
 ## `hermes kanban`
 
 ```bash
-hermes kanban <action> [options]
+hermes kanban [--board <slug>] <action> [options]
 ```
 
-Multi-profile collaboration board. Tasks live in `~/.hermes/kanban.db` (WAL-mode SQLite); every profile reads and writes the same board. A `cron`-driven dispatcher (`hermes kanban dispatch`) atomically claims ready tasks and spawns the assigned profile as its own process with an isolated workspace.
+Multi-profile, multi-project collaboration board. Each install can host many boards (one per project, repo, or domain); each board is a standalone queue with its own SQLite DB and dispatcher scope. New installs start with one board called `default`, whose DB is `~/.hermes/kanban.db` for back-compat; additional boards live at `~/.hermes/kanban/boards/<slug>/kanban.db`. The gateway-embedded dispatcher sweeps every board per tick.
 
-**This is the human / scripting surface.** Agent workers spawned by the dispatcher drive the board through a dedicated `kanban_*` [toolset](/docs/user-guide/features/kanban#how-workers-interact-with-the-board) (`kanban_show`, `kanban_complete`, `kanban_block`, `kanban_create`, `kanban_link`, `kanban_comment`, `kanban_heartbeat`) instead of shelling to `hermes kanban`. Both surfaces route through the same `kanban_db` layer, so state is consistent either way.
+**Global flags (apply to every action below):**
+
+| Flag | Purpose |
+|------|---------|
+| `--board <slug>` | Operate on a specific board. Defaults to the current board (set via `hermes kanban boards switch`, the `HERMES_KANBAN_BOARD` env var, or `default`). |
+
+**This is the human / scripting surface.** Agent workers spawned by the dispatcher drive the board through a dedicated `kanban_*` [toolset](/docs/user-guide/features/kanban#how-workers-interact-with-the-board) (`kanban_show`, `kanban_complete`, `kanban_block`, `kanban_create`, `kanban_link`, `kanban_comment`, `kanban_heartbeat`) instead of shelling to `hermes kanban`. Workers have `HERMES_KANBAN_BOARD` pinned in their env so they physically cannot see other boards.
 
 | Action | Purpose |
 |--------|---------|
 | `init` | Create `kanban.db` if missing. Idempotent. |
-| `create "<title>"` | Create a new task. Flags: `--body`, `--assignee`, `--parent` (repeatable), `--workspace scratch\|worktree\|dir:<path>`, `--tenant`, `--priority`. |
-| `list` / `ls` | List tasks. Filter with `--mine`, `--assignee`, `--status`, `--tenant`, `--archived`, `--json`. |
+| `boards list` / `boards ls` | List all boards with task counts. `--json`, `--all` (include archived). |
+| `boards create <slug>` | Create a new board. Flags: `--name`, `--description`, `--icon`, `--color`, `--switch` (make active). Slug is kebab-case, auto-downcased. |
+| `boards switch <slug>` / `boards use` | Persist `<slug>` as the active board (writes `~/.hermes/kanban/current`). |
+| `boards show` / `boards current` | Print the currently-active board's name, DB path, and task counts. |
+| `boards rename <slug> "<name>"` | Change a board's display name. Slug is immutable. |
+| `boards rm <slug>` | Archive (default) or hard-delete a board. `--delete` skips the archive step. Archived boards move to `boards/_archived/<slug>-<ts>/`. Refused for `default`. |
+| `create "<title>"` | Create a new task on the active board. Flags: `--body`, `--assignee`, `--parent` (repeatable), `--workspace scratch\|worktree\|dir:<path>`, `--tenant`, `--priority`, `--triage`, `--idempotency-key`, `--max-runtime`, `--skill` (repeatable). |
+| `list` / `ls` | List tasks on the active board. Filter with `--mine`, `--assignee`, `--status`, `--tenant`, `--archived`, `--json`. |
 | `show <id>` | Show a task with comments and events. `--json` for machine output. |
 | `assign <id> <profile>` | Assign or reassign. Use `none` to unassign. Refused while task is running. |
-| `link <parent> <child>` | Add a dependency. Cycle-detected. |
+| `link <parent> <child>` | Add a dependency. Cycle-detected. Both tasks must be on the same board. |
 | `unlink <parent> <child>` | Remove a dependency. |
 | `claim <id>` | Atomically claim a ready task. Prints resolved workspace path. |
 | `comment <id> "<text>"` | Append a comment. The next worker that claims the task reads it as part of its `kanban_show()` response. |
-| `complete <id>` | Mark task done. Flag: `--result "<summary>"` (goes into children's parent-result context). |
+| `complete <id>` | Mark task done. Flags: `--result`, `--summary`, `--metadata`. |
 | `block <id> "<reason>"` | Mark task blocked. Also appends the reason as a comment. |
 | `unblock <id>` | Return a blocked task to ready. |
 | `archive <id>` | Hide from default list. `gc` will remove scratch workspaces. |
 | `tail <id>` | Follow a task's event stream. |
-| `dispatch` | One dispatcher pass. Flags: `--dry-run`, `--max N`, `--json`. |
+| `dispatch` | One dispatcher pass on the active board. Flags: `--dry-run`, `--max N`, `--json`. |
 | `context <id>` | Print the full context a worker would see (title + body + parent results + comments). |
 | `gc` | Remove scratch workspaces for archived tasks. |
 
-All actions are also available as a slash command in the gateway (`/kanban …`), with the same argument surface.
+Examples:
+
+```bash
+# Create a second board and put a task on it without switching away.
+hermes kanban boards create atm10-server --name "ATM10 Server" --icon 🎮
+hermes kanban --board atm10-server create "Restart server" --assignee ops
+
+# Switch the active board for subsequent calls.
+hermes kanban boards switch atm10-server
+hermes kanban list                  # shows atm10-server tasks
+
+# Archive a board (recoverable) or hard-delete it.
+hermes kanban boards rm atm10-server
+hermes kanban boards rm atm10-server --delete
+```
+
+Board resolution order (highest precedence first): `--board <slug>` flag → `HERMES_KANBAN_BOARD` env var → `~/.hermes/kanban/current` file → `default`.
+
+All actions are also available as a slash command in the gateway (`/kanban …`), with the same argument surface — including `boards` subcommands and the `--board` flag.
 
 For the full design — comparison with Cline Kanban / Paperclip / NanoClaw / Gemini Enterprise, eight collaboration patterns, four user stories, concurrency correctness proof — see `docs/hermes-kanban-v1-spec.pdf` in the repository or the [Kanban user guide](/docs/user-guide/features/kanban).