feat(FN-1122): add agent permission access APIs

- Define canonical agent permission types and export permission helpers from @fusion/core
- Add permission normalization and access-state computation with role defaults plus explicit grants
- Extend AgentStore with getAccessState and add unit tests for permission logic and store behavior
- Add dashboard routes for GET /api/agents/:id/access and PATCH /api/agents/:id/permissions with request validation and serialization
- Add a minor changeset for @gsxdsm/fusion documenting the new agent permission endpoints

.changeset/fn-1122-agent-permissions.md

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+---
+"@gsxdsm/fusion": minor
+---
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+Add agent permissions and access control: structured permission model with role-based defaults, `AgentAccessState` type, `GET /api/agents/:id/access` and `PATCH /api/agents/:id/permissions` endpoints.