coder(providers): v2.3 provider-lifecycle phase 4 — config HTTP API (diagnostic returns JSON)

GET/PATCH /api/providers/config, subset POST /refresh, and
GET /api/providers/:id/diagnostic (JSON { diagnostic }, §6.4). PATCH order
is validate→save→reload→clear; a malformed body or invalid merged config
returns 422 without writing, and a save failure returns 500 without
reloading (no file/registry divergence). Web client + types extended.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/api/client.ts

@@ -14,6 +14,8 @@ import type {
   AskUserAnswer,
   ToolCostStat,
   ProviderSnapshotEntry,
+  CoderProvidersFile,
+  ProviderConfigPatch,
   CoderSendMessageBody,
   CoderSendMessageResponse,
   CoderMessageWire,
@@ -310,8 +312,23 @@ export const api = {
       const qs = cwd ? `?cwd=${encodeURIComponent(cwd)}` : '';
       return request<ProviderSnapshotEntry[]>(`/api/coder/providers/snapshot${qs}`);
     },
-    refreshProviders: () =>
-      request<{ refreshed: number }>('/api/coder/providers/refresh', { method: 'POST' }),
+    // v2.3 Phase 4: optional subset narrows the reported `refreshed` count.
+    refreshProviders: (providers?: string[]) =>
+      request<{ refreshed: number }>('/api/coder/providers/refresh', {
+        method: 'POST',
+        ...(providers && providers.length > 0 ? { body: JSON.stringify({ providers }) } : {}),
+      }),
+    // v2.3 Phase 4: read/patch the provider config file. PATCH returns the new
+    // config; a `null` value in the patch deletes that id's override.
+    getProvidersConfig: () => request<CoderProvidersFile>('/api/coder/providers/config'),
+    patchProvidersConfig: (patch: ProviderConfigPatch) =>
+      request<{ ok: true } & CoderProvidersFile>('/api/coder/providers/config', {
+        method: 'PATCH',
+        body: JSON.stringify(patch),
+      }),
+    // v2.3 Phase 4: per-provider diagnostic — JSON { diagnostic: string } (§6.4).
+    getProviderDiagnostic: (id: string) =>
+      request<{ diagnostic: string }>(`/api/coder/providers/${encodeURIComponent(id)}/diagnostic`),
     sendMessage: (sessionId: string, body: CoderSendMessageBody) =>
       request<CoderSendMessageResponse>(`/api/coder/sessions/${sessionId}/messages`, {
         method: 'POST',