fix(examples): module/receiver/ncclfrreceiver/example_config.yaml references retired stdoutexporter + tracecore collect subcommand (RFC-0013 cleanup)

[trilamsr]

Problem

Surfaced during the A+ sweep for #454: module/receiver/ncclfrreceiver/example_config.yaml and its README reference components / subcommands retired by RFC-0013:

• exporters.stdoutexporter — retired by RFC-0013 PR-A2 (replaced by debug)
• tracecore collect --config … in module/receiver/ncclfrreceiver/README.md — collect subcommand was deleted in PR-A2 (the OCB binary takes --config= directly)

`tracecore validate --config=module/receiver/ncclfrreceiver/example_config.yaml` fails on the unknown stdoutexporter reference.

Not in scope for #454 (which was scoped to docs/examples/with-telemetry.yaml). Filed separately so the operator-facing receiver README + example also tracks the post-pivot shape.

Scope

• Swap stdoutexporter → debug (with verbosity: detailed) in module/receiver/ncclfrreceiver/example_config.yaml.
• Update the tracecore collect … invocation in module/receiver/ncclfrreceiver/README.md to ./_build/tracecore --config ….
• Verify ./_build/tracecore validate --config=module/receiver/ncclfrreceiver/example_config.yaml exits 0.

Also worth checking

• docs/examples/prometheus-alerts.example.yaml mentions stdoutexporter in a regex example string (line 29). The file is structurally fine (it's a Prometheus rules file, not a collector config), but the comment is stale post-pivot and could just say otlphttp|debug.

Refs

• fix(examples): with-telemetry.yaml references retired clockreceiver + stdoutexporter (RFC-0013 cleanup) #454 (sibling issue, fixed)
• RFC-0013 PR-A2 (subcommand surface), PR-E (clockreceiver→hostmetrics swap)