Locked Edit in sandbox with upsell (plans without sandboxes)

[elias-ba]

As a workflow builder on a plan without sandboxes, I want to see "Edit in sandbox" present but locked with a clear upsell when I open a live workflow, so that I discover the safe editing path exists and how to unlock it, instead of only ever seeing Switch to draft.

Context

On plans where sandboxes are not available, a live workflow is read-only on main and the sanctioned way to change it is Switch to draft, which takes the workflow offline. The intended experience (see the epic and the design walkthrough) also keeps "Edit in sandbox" visible but locked, with an always-visible upsell tooltip, so users on smaller plans discover the paid capability rather than it being hidden.

Today the "Edit in sandbox" action is only rendered for live, non-sandbox workflows and is not gated by permission or plan on the client. PR #4901 deliberately deferred the client-side gating because it needs a permission/limit flag exposed on the session context.

Acceptance criteria

• On a plan without sandbox access, a live workflow shows "Edit in sandbox" in a locked state.
• Hovering the locked action shows an always-visible upsell tooltip.
• The upsell copy comes from the usage-limiting extension, not hardcoded in the editor.
• Switch to draft remains the working fallback alongside the locked action.
• Users with sandbox access see the action fully enabled (no regression).

Key surfaces

Collaborative editor Header, session context (new permission/limit flag), usage-limiting extension (UsageLimiting.limit_action/2).

Part of #4852.