Per-session agent config moves up to the parent agent

What changed

Cognitive config (mcps, allowedTools, configuration — permission mode, max turns, env vars, soul/scheduler/heartbeat toggles) now lives on the agent, not the session. v1 stored these on every session row; the v1 → v2 migration carries them forward only on the parent agent and drops every per-session override.

agent_session keeps just identity + naming + workspace binding + ordering — no MCP allowlist, no tool allowlist, no permission mode, no scheduler config.

Why this matters to the user

If a user customized MCP servers, allowed tools, permission mode, or the soul/scheduler/heartbeat settings on a specific session (not on the parent agent), that override does not survive the upgrade. Every migrated session falls back to whatever the parent agent has configured.

Visible places:

• Session settings panel: per-session controls for MCP / allowed-tools / permission mode no longer exist.
• Agent settings panel: the same controls now live here, and every session of that agent shares them.
• claude-code invocation: the session inherits the agent's settings.

What the user should do

1. After upgrading, open each agent's settings and confirm the agent carries the configuration the user wants every session of it to use.
2. For workflows that previously relied on multiple sessions of the same agent having different MCP / permission settings, split them into separate agents instead. Cloning an agent (with its config) and pointing sessions at the right clone is the v2 idiom.

Notes for release manager

Pair with 2026-05-19-agent-session-primary-workspace.md in the release note — both are the "session is now a thin handle around its parent agent" theme.

If the migrator emits warnings for non-empty per-session overrides that were dropped, surface the count so the user knows whether to audit.