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.
b2b479b40e