feat: add allowedAgents config for memory hooks

[rbutera]

Summary

• add allowedAgents?: string[] to plugin config parsing and schema
• skip auto-capture when the current sessionKey does not match an allowed agent
• skip auto-recall when the current sessionKey does not match an allowed agent
• document the new config option in the README
• add tests covering config parsing and the new capture/recall guards

Closes #27.

Behavior

When allowedAgents is omitted, behavior stays the same as today.

When allowedAgents is set, auto-capture and auto-recall only run for sessions whose sessionKey includes one of the configured agent IDs, for example agent:navi:main.

Test plan

• bun test allowed-agents.test.ts
• bun run check-types
• bun run lint

[rbutera]

Good catch - the bug is real.

When sessionKey is undefined, sessionKey?.includes(agentId) returns undefined. Array.some() treats that as falsy and returns false. The negation flips it to true, triggering the early return. Any session without a sessionKey was being silently dropped regardless of the allowedAgents config.

Fixed in the latest commit by gating the filter on sessionKey being present. Sessions without a sessionKey now fall through and are processed normally, which restores prior behavior. Also added two regression tests covering the undefined sessionKey case to prevent this coming back.

[rbutera]

Hey @Dhravya @Prasanna721, this is ready for review whenever you get a chance. CI is green, and the undefined sessionKey edge case from the Seer review is fixed with regression tests. Would love to get this merged so we can set up per-agent memory isolation. Thanks!