refactor!: Separate legacy MCP wiring from ActorsMcpServer

[jirispilka]

Why

Closes #1147. Part of #1128.

ActorsMcpServer combined two concerns: shared Apify behavior (tools, actorStore, server-mode, prompts/resources, widgets, payments, telemetry) and sessionful v1 SDK wiring (the SDK Server, request handlers, initialize, Tasks, logging, notifications, errors, transport lifecycle). PR #1143 showed that adding a second (stateless) serving unit forced the dependency direction backwards — shared tool execution reached up into the class (apifyMcpServer.server, .tools, extra, McpError). This extraction fixes the direction so #1140 can expose both protocol eras through dev_server.ts while reusing one Apify core.

Breaking: the raw v1 .server and .taskStore are no longer public on ActorsMcpServer — they move to the private adapter. Runtime-safe for apify-mcp-server-internal (it reads neither; verified against its new ActorsMcpServer(...) call sites, which use only .options.initializeRequestData, .loadToolsByName(), .loadToolsFromUrl(), .listAllToolNames(), .connect()). External TypeScript consumers touching those two members break at compile time — hence refactor!.

What changed

All v1 SDK wiring moved verbatim into a new package-private LegacyMcpServer (src/mcp/legacy_server.ts). ActorsMcpServer keeps the shared Apify behavior, constructs exactly one adapter, and delegates connect()/close() to it via a narrow LegacyMcpServerHost interface — the adapter never imports the concrete facade, and shared modules never import the adapter. Shared tool execution (tool_call_engine, tool_dispatch, tool_call_telemetry, task_execution) now takes plain values; InternalToolArgs drops extra/apifyMcpServer/mcpServer. No v2 SDK dependency and no stateless routing were added (that is #1140).

Behavior is preserved byte-for-byte: tool names, results, error codes/messages/data, notifications, Tasks, telemetry, and timing are unchanged. close() teardown is the deliberate reverse-of-connect order (close the transport, then clear the tool map).

Notes for reviewers (human-written)

The huge diff is because of server.ts -> legacy_server.ts
I checked it (also with Claude), all the changes seems to be ok.

Proof it works

A live mcpc probe built both this branch and the pre-change master server, then diffed their MCP output byte-for-byte: initialize, tools/list (all default-mode tools), prompts/list, resources/list + read, tools/call happy paths, a live Actor round-trip (call-actor → get-dataset-items → get-key-value-store-record → resources/read), every error path (invalid tool name, invalid arguments, resource 404, unknown prompt, tool-level SOFT_FAIL), logging/setLevel, and the task-mode pre-flight path were all identical (only per-run IDs/timestamps differed). The unit suite is unchanged at 1177 passed + 1 skipped, and type-check/lint/check:agents/format:check are clean.

🤖 Generated with Claude Code

https://claude.ai/code/session_017zHfSwpr57aUaxYjxAgsof

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Generated by Claude Code

[MQ37]

Approving. Verified the extraction line-by-line against master — logic, error codes, notification ordering and telemetry are preserved; build, typecheck, lint and the unit suite (1177 passed / 1 skipped) are green.

One awareness note, no changes requested: because ActorsMcpServer implements LegacyMcpServerHost, five previously-private members are now public API in the shipped .d.ts:

export declare class ActorsMcpServer implements LegacyMcpServerHost {
    get clientContext(): McpClientContext | undefined;   // was private
    resolveApifyToken(...);                              // was private
    resolveApifyClient(...);                             // was private
    promptService;                                       // was internal
    resourceService;                                     // was internal
}

Worth being aware of, since the breaking-change note only lists the removals (.server, .taskStore). I looked at the workarounds and do not want any of them here — the object-literal host factory hurts readability more than the wider surface does. Leaving it as-is deliberately.