Add environment variables configuration to OpenCode instances

- Add environment variables editor in advanced settings
- Store environment variables in global preferences
- Pass environment variables to OpenCode processes when spawning
- Display environment variables in instance information and server logs
- Fix system PATH binary handling for 'opencode' command
- Show detailed environment variable values in startup logs
- Save and restore last used binary across app restarts
- Add system PATH binary to recent binaries list when used

Features:
- Environment variables editor with add/remove functionality
- Persistent storage of environment variables across sessions
- Real-time display of active environment variables in logs
- Instance information shows configured environment variables
- Proper handling of system PATH vs custom binary paths
- Last used binary persistence and automatic restoration

src/stores/instances.ts

@@ -3,6 +3,7 @@ import type { Instance, LogEntry } from "../types/instance"
 import { sdkManager } from "../lib/sdk-manager"
 import { sseManager } from "../lib/sse-manager"
 import { fetchSessions, fetchAgents, fetchProviders } from "./sessions"
+import { preferences } from "./preferences"
 
 const [instances, setInstances] = createSignal<Map<string, Instance>>(new Map())
 const [activeInstanceId, setActiveInstanceId] = createSignal<string | null>(null)
@@ -61,7 +62,7 @@ async function createInstance(folder: string, binaryPath?: string): Promise<stri
       port,
       pid,
       binaryPath: actualBinaryPath,
-    } = await window.electronAPI.createInstance(id, folder, binaryPath)
+    } = await window.electronAPI.createInstance(id, folder, binaryPath, preferences().environmentVariables)
 
     const client = sdkManager.createClient(port)