Add adapter environment testing infrastructure

Introduce testEnvironment() on ServerAdapterModule with structured
pass/warn/fail diagnostics for all four adapter types (claude_local,
codex_local, process, http). Adds POST test-environment endpoint,
shared types/validators, adapter test implementations, and UI API
client. Includes asset type foundations used by related features.

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

server/src/adapters/http/test.ts

@@ -0,0 +1,116 @@
+import type {
+  AdapterEnvironmentCheck,
+  AdapterEnvironmentTestContext,
+  AdapterEnvironmentTestResult,
+} from "../types.js";
+import { asString, parseObject } from "../utils.js";
+
+function summarizeStatus(checks: AdapterEnvironmentCheck[]): AdapterEnvironmentTestResult["status"] {
+  if (checks.some((check) => check.level === "error")) return "fail";
+  if (checks.some((check) => check.level === "warn")) return "warn";
+  return "pass";
+}
+
+function normalizeMethod(input: string): string {
+  const trimmed = input.trim();
+  return trimmed.length > 0 ? trimmed.toUpperCase() : "POST";
+}
+
+export async function testEnvironment(
+  ctx: AdapterEnvironmentTestContext,
+): Promise<AdapterEnvironmentTestResult> {
+  const checks: AdapterEnvironmentCheck[] = [];
+  const config = parseObject(ctx.config);
+  const urlValue = asString(config.url, "");
+  const method = normalizeMethod(asString(config.method, "POST"));
+
+  if (!urlValue) {
+    checks.push({
+      code: "http_url_missing",
+      level: "error",
+      message: "HTTP adapter requires a URL.",
+      hint: "Set adapterConfig.url to an absolute http(s) endpoint.",
+    });
+    return {
+      adapterType: ctx.adapterType,
+      status: summarizeStatus(checks),
+      checks,
+      testedAt: new Date().toISOString(),
+    };
+  }
+
+  let url: URL | null = null;
+  try {
+    url = new URL(urlValue);
+  } catch {
+    checks.push({
+      code: "http_url_invalid",
+      level: "error",
+      message: `Invalid URL: ${urlValue}`,
+    });
+  }
+
+  if (url && url.protocol !== "http:" && url.protocol !== "https:") {
+    checks.push({
+      code: "http_url_protocol_invalid",
+      level: "error",
+      message: `Unsupported URL protocol: ${url.protocol}`,
+      hint: "Use an http:// or https:// endpoint.",
+    });
+  }
+
+  if (url) {
+    checks.push({
+      code: "http_url_valid",
+      level: "info",
+      message: `Configured endpoint: ${url.toString()}`,
+    });
+  }
+
+  checks.push({
+    code: "http_method_configured",
+    level: "info",
+    message: `Configured method: ${method}`,
+  });
+
+  if (url && (url.protocol === "http:" || url.protocol === "https:")) {
+    const controller = new AbortController();
+    const timeout = setTimeout(() => controller.abort(), 3000);
+    try {
+      const response = await fetch(url, {
+        method: "HEAD",
+        signal: controller.signal,
+      });
+      if (!response.ok && response.status !== 405 && response.status !== 501) {
+        checks.push({
+          code: "http_endpoint_probe_unexpected_status",
+          level: "warn",
+          message: `Endpoint probe returned HTTP ${response.status}.`,
+          hint: "Verify the endpoint is reachable from the Paperclip server host.",
+        });
+      } else {
+        checks.push({
+          code: "http_endpoint_probe_ok",
+          level: "info",
+          message: "Endpoint responded to a HEAD probe.",
+        });
+      }
+    } catch (err) {
+      checks.push({
+        code: "http_endpoint_probe_failed",
+        level: "warn",
+        message: err instanceof Error ? err.message : "Endpoint probe failed",
+        hint: "This may be expected in restricted networks; verify connectivity when invoking runs.",
+      });
+    } finally {
+      clearTimeout(timeout);
+    }
+  }
+
+  return {
+    adapterType: ctx.adapterType,
+    status: summarizeStatus(checks),
+    checks,
+    testedAt: new Date().toISOString(),
+  };
+}