Add Teams service gRPC proto (teams/v1)

[rowan-stein]

User request

Add the gRPC proto definition for the new Teams service to the API schema repo.

Specification

Create proto/agynio/api/teams/v1/teams.proto defining TeamsService with CRUD+List RPCs for all 6 team resources:

• Agents — Create, Get, Update, Delete, List (with query filter)
• Tools — Create, Get, Update, Delete, List (with type filter)
• MCP Servers — Create, Get, Update, Delete, List
• Workspace Configurations — Create, Get, Update, Delete, List
• Memory Buckets — Create, Get, Update, Delete, List
• Attachments — Create, Get, Delete, List (with 5 filters, no Update)

Conventions

• Package: agynio.api.teams.v1
• Go package: github.com/agynio/api/gen/agynio/api/teams/v1;teamsv1
• Cursor-based pagination (page_size/page_token/next_page_token)
• Enums with _UNSPECIFIED = 0 per buf STANDARD rules
• optional keyword on Update fields for partial update support
• google.protobuf.Struct for free-form JSON fields (Tool.config, WorkspaceConfig.nix)
• No graph-level overwrite or versioning methods

Key design notes

• Mirror the OpenAPI schemas at openapi/team/v1/ but as protobuf messages
• Each resource includes EntityMeta (id, created_at, updated_at)
• Must pass buf lint (STANDARD) and buf breaking against main