Declare Memory job authority explicitly

[rgjordana]

Why this change exists

This is the app-side companion to mobius-os/mobius#311.

Memory is the only official app currently selecting Möbius's scoped server-job
boundary. Its manifest used the historical boolean:

"background_agent": true

The platform now names the actual security decision directly:

"job_authority": "scoped"

The old name was misleading because platform-authority jobs can also run AI
agents, while a scoped job can run deterministic code. The important choice is
the operating-system authority granted to the job.

Change

• replace Memory's one background_agent declaration with
  job_authority: scoped;
• bump the app version from 2.2.0 to 2.2.1;
• update the manifest contract assertion.

No Memory job code, schedule, data access, provider selection, or UI behavior
changes. The resulting platform capability receipt still gives Memory the same
scoped source, storage, shared-memory, and provider-credential access.

Dependency and merge order

This PR requires the platform support in mobius-os/mobius#311.

Merge the platform change first, then this PR. Existing Memory installations
remain scoped through their stored schema-2 receipts during that interval. A
new Memory manifest must not merge first because an older platform does not
understand job_authority and could ignore the declaration.

The platform deliberately rejects background_agent after the migration rather
than maintaining two public spellings, so the two changes should be reviewed
together and released in this order.

Verification

• 46 JavaScript tests passed;
• all offline-harness phases passed;
• 67 Python tests passed;
• shell and Python syntax checks passed;
• the candidate platform validator accepts the migrated manifest;
• the candidate capability producer emits schema 3 with
  background.authority: scoped and no redundant agent boolean;
• git diff --check.