feat(pivot): RFC-0013 namespace alignment — tracecore.* → otelcol.*

[trilamsr]

Summary

The four surviving in-tree components (nccl_fr, pyspy, otlphttp, stdoutexporter) each emit self-telemetry through their own per-component MeterProvider. This PR renames their instrument names from the v0.1.x tracecore.* family to the upstream otelcol_<role>_<component>_<metric> convention so the in-tree namespace does not collide with the OCB pipeline-runtime's own otelcol_* family.

Per RFC-0013 §migration v0.1.0 row 119: "self-tel metric rename tracecore.* → otelcol_*".

Scope reduced post-PR-K.2 / PR-F.2. The four legacy in-tree receivers originally listed for rename (clockreceiver, containerstdout, k8sevents, kernelevents) plus the in-tree boot-path internals were deleted from the binary in #217 and #215 while this PR was in CI. The namespace-alignment edits to those files were dropped during the post-#217 merge; the surviving net diff covers only the four components still in the binary.

Rename matrix

OTel-dot form (Prometheus scrape renders dots as underscores):

v0.1.x instrument	post-rename instrument
tracecore.receiver.errors_total	otelcol.receiver.<name>.errors_total
tracecore.receiver.emissions_total	otelcol.receiver.<name>.emissions_total
tracecore.receiver.collection_latency_seconds	otelcol.receiver.<name>.collection_latency_seconds
tracecore.receiver.degraded_seconds_total	otelcol.receiver.<name>.degraded_seconds_total
tracecore.receiver.last_activity_unix_seconds	otelcol.receiver.<name>.last_activity_unix_seconds
tracecore.exporter.calls_total	otelcol.exporter.<name>.calls_total
tracecore.selftelemetry.init_errors_total	otelcol.selftelemetry.init_errors_total

Where <name> is the OCB component name without underscores. Per-component substitutions:

Component	<name>
components/receivers/nccl_fr	ncclfr (underscore stripped per RFC)
components/receivers/pyspy	pyspy
components/exporters/otlphttp	otlphttp
components/exporters/stdoutexporter	stdoutexporter

Label shape is preserved. component_id still partitions per-instance; kind / result values are unchanged. Dashboards and alerts that filtered on labels need only the metric-name rename, not a label-selector rewrite.

What changed

• Four selftel.go files (otlphttp, stdoutexporter, nccl_fr, pyspy) — instrument literals updated; header comments rewritten to document the new convention + label-preservation invariant.
• Four selftel_test.go files — findInstrument(..., "...") and scopeOf(..., "...") assertions updated; receiverInstrumentPrefix / exporterInstrumentPrefix constants (used by the failingReceiverMP / failingExporterMP synthetic-failure seams) bumped to the new prefix so a future drift back to tracecore.* would fail compile-time on the prefix mismatch.
• docs/examples/prometheus-alerts.example.yaml — rewritten as receiver-agnostic starter using regex matchers ({__name__=~"otelcol_receiver_.*_errors_total"}) so a new in-tree receiver inherits coverage on first scrape. Removed the tracecore_exporter_failure_rate / tracecore_build_info rules — those v0.1.x gauges no longer exist post-RFC-0013.
• docs/migration/v0.1-to-v0.2.md — new "In-tree receiver / exporter namespace alignment (RFC-0013 v0.1.0)" section listing only the four surviving in-tree components; points operators at the existing "Orphan in-tree components" table for deleted-receiver migration.
• NOTE on ExporterCarrier removal blocks in otlphttp.go + stdoutexporter.go collapsed — they referenced cmd/tracecore.collect.collectFailureRateReaders (deleted in PR-A2) and internal/selftelemetry (deleted in PR-F.1). New comments point at the PromQL recipe rate(otelcol_exporter_<name>_calls_total{result="error"}[5m]).
• CHANGELOG — [Unreleased] entry added documenting the alignment.

Test plan

• go vet ./... clean (root + module/ submodule)
• go test ./... all green (root module; module/ submodule has no test files)
• make check (fmt + tidy-check + lint + vet + mod-verify) green
• make doc-check green
• TestSelfTelemetry_* assertions pass for every surviving package
• TestFactory_FallsBackToNoopWhenMeterFails synthetic-register-failure seam still trips on the renamed prefix (failingReceiverMP / failingExporterMP)

Merge resolution (post-#215, #217)

Conflicts surfaced as "deleted by them" across 20 files in the four deleted receivers. Resolution: accept all upstream deletions; the namespace-alignment edits to those files were moot because the files themselves no longer exist on main. No content edits required to the surviving four components from the merge — their namespace-alignment commits remain intact.

**Breaking (pre-1.0)**: in-tree component self-telemetry metric names renamed from `tracecore.*` to `otelcol.<role>.<name>.*` per RFC-0013 §migration v0.1.0 namespace alignment. Affects the four surviving in-tree components (`nccl_fr`, `pyspy`, `otlphttp`, `stdoutexporter`); the four legacy in-tree receivers (`clockreceiver`, `containerstdout`, `k8sevents`, `kernelevents`) were already deleted from the binary in #215 / #217 and migrate via the upstream-receiver replacements documented in the "Orphan in-tree components" table in `docs/migration/v0.1-to-v0.2.md`. Label shape preserved (`component_id`, `kind`, `result` unchanged). Operators with dashboards / alerts on the v0.1.x names rename per the table in `docs/migration/v0.1-to-v0.2.md` under "In-tree receiver / exporter namespace alignment".