refactor(skill-mcp-manager): split manager.ts into connection and client modules

Extract MCP client lifecycle management:
- connection.ts: getOrCreateClientWithRetry logic
- stdio-client.ts, http-client.ts: transport-specific creation
- oauth-handler.ts: OAuth token management
- cleanup.ts: session and global cleanup
- connection-type.ts: connection type detection

src/features/skill-mcp-manager/http-client.ts

@@ -0,0 +1,68 @@
+import { Client } from "@modelcontextprotocol/sdk/client/index.js"
+import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js"
+import { registerProcessCleanup, startCleanupTimer } from "./cleanup"
+import { buildHttpRequestInit } from "./oauth-handler"
+import type { ManagedClient, SkillMcpClientConnectionParams } from "./types"
+
+export async function createHttpClient(params: SkillMcpClientConnectionParams): Promise<Client> {
+  const { state, clientKey, info, config } = params
+
+  if (!config.url) {
+    throw new Error(`MCP server "${info.serverName}" is configured for HTTP but missing 'url' field.`)
+  }
+
+  let url: URL
+  try {
+    url = new URL(config.url)
+  } catch {
+    throw new Error(
+      `MCP server "${info.serverName}" has invalid URL: ${config.url}\n\n` +
+      `Expected a valid URL like: https://mcp.example.com/mcp`
+    )
+  }
+
+  registerProcessCleanup(state)
+
+  const requestInit = await buildHttpRequestInit(config, state.authProviders)
+  const transport = new StreamableHTTPClientTransport(url, {
+    requestInit,
+  })
+
+  const client = new Client(
+    { name: `skill-mcp-${info.skillName}-${info.serverName}`, version: "1.0.0" },
+    { capabilities: {} }
+  )
+
+  try {
+    await client.connect(transport)
+  } catch (error) {
+    try {
+      await transport.close()
+    } catch {
+      // Transport may already be closed
+    }
+
+    const errorMessage = error instanceof Error ? error.message : String(error)
+    throw new Error(
+      `Failed to connect to MCP server "${info.serverName}".\n\n` +
+      `URL: ${config.url}\n` +
+      `Reason: ${errorMessage}\n\n` +
+      `Hints:\n` +
+      `  - Verify the URL is correct and the server is running\n` +
+      `  - Check if authentication headers are required\n` +
+      `  - Ensure the server supports MCP over HTTP`
+    )
+  }
+
+  const managedClient = {
+    client,
+    transport,
+    skillName: info.skillName,
+    lastUsedAt: Date.now(),
+    connectionType: "http",
+  } satisfies ManagedClient
+
+  state.clients.set(clientKey, managedClient)
+  startCleanupTimer(state)
+  return client
+}