Bug report: Can't share workspaces when Context is enabled for all

[twinprime19]

1. Summary

When Context (the gatekeeper) is set to Enabled for all (admin), anyone with one private collection ⇒ every workspace they have chatted in, with or without on Context connections, is unshareable, forever, with no UI hint of the cause and no UI path to clear it.

2. Symptom

Collaborator (sharee) opening a shared workspace gets a terminal error:

This workspace could not confirm that you are permitted to observe all of the data it has accessed:
Context (Context) — This collaborator does not have access to a Context collection whose data this workspace has read, so they cannot be allowed to observe it.

• Shown to the sharee (packages/workshop-frontend/src/useWorkspaceOpen.ts:151, substring-matched on permitted to observe).
• Owner sees nothing. Share appears to succeed.
• Workspace's own Connections panel shows no Context entry (ambient bindings are never listed there — see §5), so the message looks nonsensical to both parties.
• Sharee having Context "connected" is irrelevant: everyone has it under Enabled-for-all.

3. Reproduction

Preconditions

• Admin → Context ambient mode = Enabled for all (shouldAutoProvisionAccount → packages/workshop-backend/src/provisioning-policy.ts:32).
• Two users on the same deployment: A (owner), B (collaborator).
• A owns ≥1 private Context collection (Context & Skills → new collection → Private; add any one document).

Steps

1. A creates a new workspace. Content irrelevant (a static web page is enough). Do not bind or mention Context.
2. A starts one chat and sends any message ("hello"). ← poisoning step (chat seeding loads the ambient catalog).
3. A shares the workspace with B (Share modal / share link).
4. B opens the workspace.

Expected: B opens the workspace and sees the chats.
Actual: terminal error from §2.