M3: Agent bound to a seat — configure an AI seat

OrgBoard: Agent entity (name, monogram, autonomy dial, ApiConfigId + optional fallback,
skill keys, docs) + AddAgents migration; one agent per seat. References Skills by key and
the BYOK config by id — never reaches into those modules.

Endpoints: POST/GET /api/orgboard/seats (create/list seats), POST/GET
/api/orgboard/seats/{id}/agent (configure/read the agent) — ConfigureAgents at [team, org].
Configuring an agent flips the seat to the AI state and points it at the agent; audited.

Verified: build green; ArchitectureTests 8/8; IntegrationTests 27/27 incl. the M3 acceptance
flow — owner adds a BYOK config, then configures "Aria" (gated autonomy, skills, that config)
on a seat, flipping it to AI, with the key never exposed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Modules/TeamUp.Modules.OrgBoard/Persistence/Migrations/OrgBoardDbContextModelSnapshot.cs

@@ -1,5 +1,6 @@
 // <auto-generated />
 using System;
+using System.Collections.Generic;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
@@ -23,6 +24,57 @@ namespace TeamUp.Modules.OrgBoard.Persistence.Migrations
 
             NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
 
+            modelBuilder.Entity("TeamUp.Modules.OrgBoard.Domain.Agent", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("ApiConfigId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Autonomy")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)");
+
+                    b.Property<DateTimeOffset>("CreatedAtUtc")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.PrimitiveCollection<List<string>>("Docs")
+                        .IsRequired()
+                        .HasColumnType("text[]");
+
+                    b.Property<Guid?>("FallbackApiConfigId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Monogram")
+                        .HasMaxLength(8)
+                        .HasColumnType("character varying(8)");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<Guid>("SeatId")
+                        .HasColumnType("uuid");
+
+                    b.PrimitiveCollection<List<string>>("SkillKeys")
+                        .IsRequired()
+                        .HasColumnType("text[]");
+
+                    b.Property<DateTimeOffset>("UpdatedAtUtc")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("SeatId")
+                        .IsUnique();
+
+                    b.ToTable("agents", "orgboard");
+                });
+
             modelBuilder.Entity("TeamUp.Modules.OrgBoard.Domain.Organization", b =>
                 {
                     b.Property<Guid>("Id")