[rc1-prep] Delete in-tree components/exporters/otlphttp/ wrapper (superseded by upstream otlphttpexporter)

[trilamsr]

The v1.0-rc1 simplification audit
(docs/v1-rc1-simplification-audit.md)
identified components/exporters/otlphttp/ as a zero-risk deletion
candidate. The package is not wired through the OCB binary —
builder-config.yaml line 59 brings in
upstream go.opentelemetry.io/collector/exporter/otlphttpexporter v0.130.0 instead. The in-tree wrapper has no Go importers outside
its own _test.go files.

Per docs/followups/otlphttp.md:

wrapper-touching items become [STRIKE] — upstream
otlphttpexporter already provides these surfaces, and the
wrapper's audit trail closes when the wrapper is deleted.

Numbers

• Total LOC: 2,904 across 11 files (find components/exporters/otlphttp -name "*.go" | xargs wc -l)
• Non-test LOC: 1,168
• External Go importers: 0 (grep -rln 'github.com/tracecoreai/tracecore/components/exporters/otlphttp' --include="*.go" . | grep -v components/exporters/otlphttp/)

Verification steps before deletion

• Confirm _build/components.go does not reference the in-tree
  wrapper (currently it does not)
• Confirm make build still produces a working _build/tracecore
  after the directory is removed
• Confirm make ci passes (no test under ./... imports the wrapper)
• Confirm make coverage-check still passes after dropping the
  components/exporters/otlphttp coverage row (the upstream
  exporter is not policed for coverage)
• Update docs/FAILURE-MODES.md test
  citations that point at wrapper tests
  (components/exporters/otlphttp/otlphttp_test.go::TestExporter_RetriesOnNetworkError,
  etc.) — re-point to upstream otlphttpexporter upstream tests
  or move the failure-mode rows to "covered upstream"
• Update docs/README.md to drop the wrapper
  README row (line 77)
• Update docs/STRATEGY.md §"Each component
  owns its own Factory var" if it references the wrapper
• Mark every [STRIKE] item in docs/followups/otlphttp.md as
  satisfied (or delete the shard outright if every row is [STRIKE])
• Remove the components/exporters/otlphttp/** triggers from
  .github/workflows/install-bench.yml lines 16, 26
• Run register-lint (make register-lint) to confirm no
  stale-allowlist row needs removing
• Update MILESTONES.md M5 row if it cites the
  in-tree wrapper

Risk score

1 (zero risk). No Go importers, no operator-visible surface,
upstream replacement already in the OCB build.