[rc1-prep] test-gap: add ncclfrreceiver end-to-end integration test

[trilamsr]

Context

Audit in docs/v1-rc1-test-audit.md §3.

The NCCL FR receiver is the moat's flagship receiver. Today:

• FuzzParseFRPickle covers the safe-pickle parser.
• nccl_fr_test.go covers emit in isolation.
• No test wires the full receiver factory → file-watch → emit-to-consumer chain against a binary .pkl fixture.

Fix

Add module/receiver/ncclfrreceiver/nccl_fr_integration_test.go that:

1. Instantiates the receiver via its factory + a real componenttest.NewNopHost.
2. Points the watch path at a temp dir.
3. Drops one of the committed .pkl fixtures from module/pkg/nccl/fr_parser/testdata/ into the dir.
4. Asserts the consumer receives exactly one emit, the resource attributes carry nccl.fr.source_path, and selftel IncEmissions fired once.

Use the upstream consumertest.LogsSink shape that pyspy/integration_helper_test.go already follows for the precedent.

Acceptance

• New test passes under -race.
• Skips cleanly on Windows if hostpath behaviour diverges (use //go:build !windows only if necessary).

Effort

M (~1 day). Adopt-over-build: upstream componenttest + consumertest.