Plan integration 6: Launch planning-purpose agent sessions

[NetDevAutomate]

Parent

• Integrate Study Plans across Now, Web architect, and MCP #7 — Integrate Study Plans across Now, Web architect, and MCP

What to build

Allow the backend to launch the Study Plan Architect through the existing session claim, agent adapter, PTY/ACP transport, reconnect, and cleanup machinery.

Acceptance criteria

• Session launch accepts planning purpose while normal study remains the default.
• Planning purpose selects the architect persona, shared protocol, and evidence-grounded planning brief.
• PTY and ACP launch paths use one purpose/persona resolver.
• Starting an architect conversation creates no plan and stores no live-session plan identifier.
• Existing one-session conflict, reconnect, error, and cleanup behavior is preserved.
• The architect can use MCP authoring tools with the CLI retained as a harness fallback.

Blocked by

• Plan integration 2: Centralize mutations and checkpoints #9 — Plan integration 2: Centralize mutations and checkpoints
• Plan integration 4: Add MCP discovery and authoring #11 — Plan integration 4: Add MCP discovery and authoring

Definition of Done

• Fake-agent tests cover successful planning launch without paid model calls.
• Session-authority and PTY/ACP transport suites remain green.
• Planning-purpose reconnect state is externally observable and documented.
• No second session authority, transport stack, or console implementation is introduced.
• Agent-adapter and live-session capability specs are updated.