v1.14.1-mcp-poc: single-server MCP client against Context7

Validates the MCP-client loop end-to-end against one real MCP server before
the full v1.15 port. New services/mcp-client.ts wraps @modelcontextprotocol/sdk
v1.29.0 with Streamable HTTP transport. On startup (when MCP_CONTEXT7_URL is
set), connects to Context7, discovers tools via tools/list, wraps each as a
ToolDef prefixed context7_<name>, and appends to ALL_TOOLS via appendMcpTools.

Read-only invariant guard rejects any tool with readOnlyHint: false. Tool
dispatch is transparent — executeToolCall routes MCP calls through the ToolDef
execute wrapper, which strips the prefix before calling the MCP server. Result
size capped at 5MB with truncation. Graceful degradation: server down at
startup → zero tools; server down mid-session → error result, model
self-corrects.

Adversarial review caught that a Zod .default() on the URL config made MCP
always-on instead of opt-in — fixed by removing the default. MCP_CONTEXT7_URL
must be explicitly set to enable.

ALL_TOOLS changed from ReadonlyArray to mutable to support late-registration.
appendMcpTools re-sorts and rebuilds TOOLS_BY_NAME after append.

348/348 server tests passing (16 new mcp-client tests). No schema changes,
no frontend changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/server/src/config.ts

@@ -19,6 +19,10 @@ const ConfigSchema = z.object({
   GITEA_USER: z.string().default('indifferentketchup'),
   GITEA_TOKEN: z.string().optional(),
   GITEA_SSH_HOST: z.string().default('100.114.205.53:2222'),
+  // v1.14.1-mcp-poc: Context7 MCP server. Streamable HTTP transport.
+  // Set to empty string or omit to disable MCP tools entirely.
+  MCP_CONTEXT7_URL: z.string().optional(),
+  MCP_CONTEXT7_API_KEY: z.string().optional(),
 });
 
 export type Config = z.infer<typeof ConfigSchema>;