v1.15.0-mcp-multi: multi-server MCP client + stdio transport + config file + tool globs

Generalizes the v1.14.1 single-server Context7 PoC into a multi-server MCP
client registry with per-server graceful degradation. JSON config at
/data/mcp.json (bind-mounted alongside AGENTS.md) matches opencode's
mcpServers schema shape. Config file missing = no MCP (opt-in by presence).

Two transports: Streamable HTTP (remote servers like Context7) and stdio
(local subprocess servers like codecontext). Stdio spawns a persistent child
via the SDK's StdioClientTransport; shutdown hook closes all transports.

Tool prefix generalized from context7_<name> to <serverName>_<toolName> with
a toolToServer reverse map for dispatch routing. AGENTS.md tools: field now
supports glob patterns (context7_*, !web_*) via matchToolGlob — last-match-
wins with ! deny prefix. Replaces exact-match .includes() in stream-phase.ts.

refreshToolNames() in agents.ts rebuilds the DEFAULT_TOOLS snapshot after
appendMcpTools so agents without explicit tools: lists see MCP tools —
reviewer caught that the module-load-time snapshot would permanently exclude
late-registered tools.

Read-only invariant: readOnlyHint === false rejected at discovery. Result
size capped at 5MB. v1.14.1 env vars removed — superseded by config file.
Default data/mcp.json ships with Context7 disabled.

363/363 server tests passing. No schema changes, no frontend changes.

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

data/mcp.json

@@ -0,0 +1,9 @@
+{
+  "mcpServers": {
+    "context7": {
+      "type": "streamableHttp",
+      "url": "https://mcp.context7.com/mcp",
+      "enabled": false
+    }
+  }
+}