Port `worksheet` CRUD commands from the Go fork

[beengud]

Port worksheet CRUD commands from the Go fork

Source: beengud/observe PR #7. Files: cmd_worksheet.go, ot_worksheet.go.
New CLI status: Absent.

Old command surface

observe worksheet list [--name <filter>]   # list worksheets in workspace; --name = case-insensitive substring
observe worksheet get <id>                  # fetch one worksheet as JSON incl. stages (stageID, pipeline)
observe worksheet create <file.json>        # create from WorksheetInput JSON (name, workspaceId, stages required)
observe worksheet delete <id>               # delete; prints confirmation

Global --workspace selects the workspace. Stages are { stageID, pipeline }.

Porting notes ⚠️

• Same stageID/stageId normalization caveat as board/dataset applies to worksheet stage inputs.

Acceptance

• list/get/create/delete ported with --name filter and --format support; tests ported.