docs: command references for beta.3

[pacphi]

Why

Guides name retired commands (ledger section E).

In scope

Update the README command section, providers.md, hooks.md and maintenance.md.

Out of scope

Dashboard docs (#377).

Acceptance criteria

• No guide names a retired command

Dependencies

Blocked by: #360

Blocks: #383, #387

Plan

• Release: 4.0.0-beta.3
• Size: size:M · Workstream: ws:ga-readiness
• Epic: feat: project-scope P5, sync, status, uninstall and the command folds (epic) #300
• Card: P5-09 in the card inventory
• Sources: Supersession ledger (docs(plans): v4 GA master plan, supersession ledger and v5 registers #290) section E

Verification

• pnpm run lint:md