Initial package implementation: operations registry, call protocol, and adapters

Extracted from alkhub_ts packages/core/operations/ and packages/core/mcp/.
- Runtime-agnostic (injected fs/env deps, no Deno globals)
- Direct @logtape/logtape import instead of logger wrapper
- PendingRequestMap with pubsub-wired call protocol
- Peer-dep isolation for MCP adapter (sub-path export)
- Schema const naming convention (XSchema + X type alias)
- 68 tests passing, build + lint + test all green

docs/architecture/decisions/003-peer-dep-adapters.md

@@ -0,0 +1,54 @@
+# ADR-003: Peer Dependencies for Adapter Isolation
+
+**Status**: Accepted
+**Date**: 2026-04-30
+
+## Context
+
+The MCP adapter (`from_mcp.ts`) depends on `@modelcontextprotocol/sdk` for `Client`, `StdioClientTransport`, and `StreamableHTTPClientTransport`. This dependency is heavy (transitive deps) and only needed by consumers that connect to MCP servers. Other adapters may have similar heavy dependencies in the future (e.g., gRPC, GraphQL).
+
+Two approaches:
+
+1. **Regular dependency** — list `@modelcontextprotocol/sdk` as a direct dependency. All consumers install it.
+2. **Optional peer dependency + sub-path export** — list it as an optional peer dependency, import dynamically, and expose via a separate `./from-mcp` sub-path export.
+
+## Decision
+
+Use optional peer dependency with sub-path export.
+
+```json
+{
+  "peerDependencies": {
+    "@modelcontextprotocol/sdk": "^1.0.0"
+  },
+  "peerDependenciesMeta": {
+    "@modelcontextprotocol/sdk": { "optional": true }
+  },
+  "exports": {
+    ".": { ... },
+    "./from-mcp": { ... }
+  }
+}
+```
+
+## Rationale
+
+1. **Zero-cost for non-MCP consumers** — `npm install @alkdev/operations` does not install `@modelcontextprotocol/sdk`. Only consumers that `import { createMCPClient } from "@alkdev/operations/from-mcp"` need to install it.
+
+2. **Dynamic import** — `from_mcp.ts` uses `await import("@modelcontextprotocol/sdk/client/index.js")` and `await import("@modelcontextprotocol/sdk/client/stdio.js")`. The MCP SDK is loaded only when `createMCPClient` is actually called, not at module parse time.
+
+3. **Explicit dependency declaration** — the sub-path import makes it clear at the import site that this code needs the MCP SDK. A barrel-only import doesn't communicate this.
+
+4. **No bundler reliance** — sub-path exports don't depend on the consumer's bundler correctly tree-shaking. Not all consumers use bundlers (Deno, Node with `--experimental-strip-types`).
+
+5. **Follows established pattern** — `@alkdev/pubsub` uses the same approach for its Redis adapter (sub-path export with optional ioredis peer dep).
+
+6. **Incremental** — future adapters (gRPC, GraphQL) will follow the same pattern. Each adds one peer dep entry and one sub-path export.
+
+## Consequences
+
+- `package.json` has a peer dep entry for each adapter's external dependency
+- Both barrel and sub-path work — barrel re-exports everything for convenience, sub-path for explicitness
+- `tsup` must list each adapter as a separate entry point
+- Consumer docs should recommend sub-path imports for adapter-specific code
+- The `from_mcp.ts` module also imports from `from_schema.ts` and `types.ts` (core), which are bundled into the sub-path output by tsup's code splitting