feat: persistence and lifecycle improvements for Modus Agents

[mattjohnsonpint]

This PR layers on to #840 to add persistence of Modus Agents. It also improves the agent lifecycle events and APIs, so they match the agent's state changes.

Agent state is persisted to ModusGraph (previously ModusDB) in local development. In production, it's persisted to the backend's PostgresDB instance that has already been configured.

With these changes, you can completely shut down and restart the runtime without losing any agent state.

[linear]

HYP-3347 Persist agent state between Actor / Runtime restarts

[trunk-io]

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[Copilot]

Pull Request Overview

Adds durable persistence and refined lifecycle hooks for Modus Agents, enabling full shutdown and restart without losing state.

• Introduces new onSuspend, onRestore, and onTerminate hooks and updates AssemblyScript agent APIs
• Persists agent state to ModusGraph in dev and Postgres in production, with migrations
• Updates Go actor system to reload and respawn agents based on stored state

Reviewed Changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
sdk/assemblyscript/src/assembly/enums.ts	Updated agent status enum values
sdk/assemblyscript/src/assembly/agent.ts	Added terminateAgent, updated shutdownAgent, hooks, constructor default
sdk/assemblyscript/src/assembly/agents.ts	Exported terminate from agent module
sdk/assemblyscript/examples/agents/assembly/index.ts	Example terminateAgent function added
sdk/assemblyscript/examples/agents/assembly/counterAgent.ts	Implemented new lifecycle hooks in example agent
runtime/hostfunctions/agents.go	Registered terminateAgent host function
runtime/db/modusdb.go	Switched to modusgraph import and config logic
runtime/db/db.go	Added useModusDB toggle function
runtime/db/agentstate.go	New persistence logic for agent state
runtime/db/migrations/000007_add_agent_state.up.sql	Migration to create agents table
runtime/db/migrations/000007_add_agent_state.down.sql	Migration to drop agents table
runtime/actors/agents.go	Added TerminateAgent, status tracking, respawn logic
runtime/actors/actorsystem.go	Reload and respawn agents at startup
go.mod & go.work	Dependency bumped to modusgraph and other modules
CHANGELOG.md	Added entry for persistence and lifecycle improvements
.trunk/configs/cspell.json	Added "modusgraph" to dictionary