Port `board` (dashboard) commands from the Go fork

[beengud]

Port board (dashboard) commands from the Go fork

Source: beengud/observe PR #2 (board CRUD) + PR #9 (visibility/folderId fields, view URL output). Files: cmd_board.go, ot_board.go, cmd_board_*_test.go.
New CLI status: Absent — no board/dashboard commands exist.

Old command surface

observe board create <file.json>          # create board from DashboardInput JSON (name, workspaceId, layout required; stages optional)
observe board update <id> <file.json>      # update existing board; sets id from arg
observe board scaffold [--name NAME]       # print minimal board template JSON to stdout
observe board set-default <id>             # set a default board
observe board clear-default                # clear the default board
observe list board [--name <f>] [--folder <id>]   # via generic object layer
observe get board <id>
observe delete board <id>

Flags: --name (filter when listing / set name when scaffolding), --folder (filter by folder ID).

Behavior / API

• Backed by saveDashboard GraphQL mutation and dashboard queries.
• PR Port RBAC support + rbac-dot from the Go fork #9 added board visibility and folderId fields and printed the view URL for the board after create/update.

Porting notes ⚠️

• Re-apply the stage normalization workarounds from PR feat(schema): port schema introspect from Go CLI #11 and follow-up commits: normalize stageID→id, stageId, and inputRole in board stage objects before calling saveDashboard, or you get null-schema violations. See old commits 49fc439, 73979a4/44e2ded, 3ad36f0/59e70dd.
• Confirm current DashboardInput shape against the live schema (the old schema introspect command — see its issue — was built specifically to chase Dashboard field drift).

Acceptance

• board create/update/scaffold + default management ported with --format support and view-URL output, matching old behavior; tests ported.