feat(pins): add ipfs_pin_count tool and limit/offset pagination for ipfs_list_pins

[karawitan]

Summary

Nodes with large pinsets (hundreds of thousands to millions of pins) make the current ipfs_list_pins tool impractical: it materializes the full pinset and returns every CID through the MCP channel — huge memory spikes, tool timeouts, and blown agent context.

• New ipfs_pin_count MCP tool — streams Kubo pin/ls --type=all --stream and returns only counts by type (direct, recursive, indirect, total). Constant memory: no CIDs are accumulated, safe for pinsets of any size.
• ipfs_list_pins pagination — new optional limit/offset params. When limit is set, iteration stops early instead of draining the stream. Response now includes count (and limit/offset when given).
• Core additions, exposed through the whole stack:
  • MeshkitClient.countPins(): Promise<PinCount> (new PinCount type)
  • MeshkitClient.listPins(options?: ListPinsOptions)
  • Meshkit.countPins() / Meshkit.listPins(options) (primary node)
  • fil.one/S3 client: countPins = stored object count, pagination via slice
  • exported countPinsViaRpc / applyPinLsLine helpers from @ipfs-meshkit/core

Implementation notes

• countPinsViaRpc POSTs /api/v0/pin/ls?type=all&stream=true and tallies the NDJSON stream line-by-line (handles the streamed {"Cid":...,"Type":...} format and the legacy Keys mapping; the legacy type-less Pins array is ignored). Optional auth headers from the node config are forwarded.
• listPins({limit, offset}) on Kubo skips offset entries then stops the async iterator as soon as limit CIDs are collected.

Test plan

• 224 unit tests pass (vitest run --project unit), including new tests: pin-count.test.ts (line tallying, chunk-boundary splits, legacy formats, HTTP errors), create-client.test.ts (early-stop pagination, offset skip, count via client), meshkit.test.ts (primary-node-only, option passthrough), storage.test.ts (MCP handlers)
• tsc --noEmit clean; npm run build + mcp build succeed
• Live-tested against a Kubo node with a 1M+ pinset: ipfs_list_pins {limit:2, offset:1} returns instantly; ipfs_pin_count streams without unbounded memory growth

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