feat: add agent icons with picker and collapsible sidebar section

- Add `icon` text column to agents DB schema with migration
- Add icon field to shared Agent type and validators
- Create AgentIconPicker component with 40+ curated lucide icons and search
- Show clickable icon next to agent name on detail page header
- Replace static Agents nav item with collapsible AGENTS section in sidebar
- Each agent shows its icon (defaulting to Bot) with truncated name

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/db/src/migrations/0016_agent_icon.sql

@@ -0,0 +1 @@
+ALTER TABLE "agents" ADD COLUMN "icon" text;

packages/db/src/migrations/meta/_journal.json

@@ -113,6 +113,13 @@
       "when": 1771865100000,
       "tag": "0015_project_color_archived",
       "breakpoints": true
+    },
+    {
+      "idx": 16,
+      "version": "7",
+      "when": 1771955900000,
+      "tag": "0016_agent_icon",
+      "breakpoints": true
     }
   ]
 }

packages/db/src/schema/agents.ts

@@ -18,6 +18,7 @@ export const agents = pgTable(
     name: text("name").notNull(),
     role: text("role").notNull().default("general"),
     title: text("title"),
+    icon: text("icon"),
     status: text("status").notNull().default("idle"),
     reportsTo: uuid("reports_to").references((): AnyPgColumn => agents.id),
     capabilities: text("capabilities"),

packages/shared/src/types/agent.ts

@@ -14,6 +14,7 @@ export interface Agent {
   name: string;
   role: AgentRole;
   title: string | null;
+  icon: string | null;
   status: AgentStatus;
   reportsTo: string | null;
   capabilities: string | null;

packages/shared/src/validators/agent.ts

@@ -27,6 +27,7 @@ export const createAgentSchema = z.object({
   name: z.string().min(1),
   role: z.enum(AGENT_ROLES).optional().default("general"),
   title: z.string().optional().nullable(),
+  icon: z.string().optional().nullable(),
   reportsTo: z.string().uuid().optional().nullable(),
   capabilities: z.string().optional().nullable(),
   adapterType: z.enum(AGENT_ADAPTER_TYPES).optional().default("process"),