v2.1.0-provider-picker: BooCoder systemd migration + provider picker

- BooCoder moves from Docker to host systemd service (boocoder.service)
- Agent dispatch (ACP + PTY) switches from SSH to direct spawn/exec
- SSH helpers marked @deprecated (kept for one release cycle)
- Provider registry (5 providers: boocode, opencode, goose, claude, qwen)
- Agent probe with direct which/exec + model discovery (qwen settings, static claude models)
- GET /api/providers route with installed status, models, transport fallback
- ProviderPicker frontend component in CoderPane header
- External provider messages route through tasks row instead of inference enqueue
- Smart scroll: MessageList only auto-scrolls when near bottom (150px threshold)
- DB: available_agents gets models, label, transport columns
- Bug fix: loadContext SELECT includes allowed_read_paths
- Bug fix: cap hit sentinel inserted before buildMessagesPayload
- docker-compose.yml: boocoder service commented out, BOOCODER_URL env var added
- CLAUDE.md: updated docs for systemd, provider registry, JSONB gotcha, loadContext

apps/web/src/api/client.ts

@@ -13,6 +13,7 @@ import type {
   Skill,
   AskUserAnswer,
   ToolCostStat,
+  Provider,
 } from './types';
 
 export class ApiError extends Error {
@@ -298,6 +299,10 @@ export const api = {
 
   models: () => request<ModelInfo[]>('/api/models'),
 
+  coder: {
+    providers: () => request<Provider[]>('/api/coder/providers'),
+  },
+
   agents: {
     list: (projectId: string) =>
       request<AgentsResponse>(`/api/projects/${projectId}/agents`),