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Expose MessageInfo metadata on subscription callbacks (#1440)

Exposes ROS 2 message metadata (timestamps, sequence numbers, publisher GID) to subscription callbacks, matching rclpy's `MessageInfo` pattern. When a subscription callback declares two parameters, it automatically receives a `MessageInfo` object as the second argument containing metadata from the middleware layer. Single-parameter callbacks are unchanged — no performance overhead, full backward compatibility.

**New files:**

- `lib/message_info.js` — `MessageInfo` class wrapping native `rmw_message_info_t` fields: `sourceTimestamp` (bigint), `receivedTimestamp` (bigint), `publicationSequenceNumber` (bigint), `receptionSequenceNumber` (bigint), `publisherGid` (Buffer). Includes `toPlainObject()` helper.
- `types/message_info.d.ts` — Full TypeScript declarations for `MessageInfo`.
- `test/test-message-info.js` — 6 tests covering: MessageInfo delivery with 2-param callbacks, non-delivery with 1-param callbacks, timestamp validity, timestamp ordering, `toPlainObject()`, and export verification.

**Modified files:**

- `src/rcl_subscription_bindings.cpp` — Added `RclTakeWithInfo()` native function that calls `rcl_take()` with `rmw_message_info_t` (instead of `nullptr`) and returns a JS object with all metadata fields as BigInts and a GID Buffer. Registered as `rclTakeWithInfo` binding. Added `#include <rmw/types.h>`.
- `lib/subscription.js` — Added `_wantsMessageInfo` flag detected via `callback.length >= 2`. Added `wantsMessageInfo` readonly getter. Updated `processResponse()` to accept optional `messageInfo` second parameter and forward it to the callback when the flag is set.
- `lib/node.js` — Updated subscription spin loop: when `subscription.wantsMessageInfo` is true, uses `rclTakeWithInfo` and wraps the result in `MessageInfo`; otherwise uses the existing `rclTake` path (zero overhead for 1-param callbacks). Added `MessageInfo` require.
- `index.js` — Exported `MessageInfo` class.
- `ty... (continued)

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