ci: Add OpenTelemetry span-attribute naming check (phase 1c)

Add check_otel_naming.py and wire it into on-pr.yml so every PR validates
that span-attribute names stay consistent across the code, collector, Tempo,
dashboards, and docs.

- The valid key set is derived dynamically from the *SpanNames.h constants and
  the resource attributes the code registers in Telemetry.cpp — no hardcoded
  allowlist to drift.
- Each rule is presence-gated: it runs only when the file it needs is in the
  tree, so the check is correct whether telemetry changes land in one PR or
  several (the collector/Tempo/dashboard/runbook layers arrive in later phases).
- Rule A flags dotted span-attribute keys; Rule F flags string-literal
  attribute keys and span-name arguments (values may be runtime data).
- stdlib-only, mirroring the levelization check (bare `python`, no pip step).
- Telemetry.h / SpanGuard.h @code examples now use *SpanNames.h constants so
  the strict literal check passes.
- CONTRIBUTING.md documents the check and how to run it locally.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/on-pr.yml

@@ -51,8 +51,10 @@ jobs:
           files: |
             # These paths are unique to `on-pr.yml`.
             .github/scripts/levelization/**
+            .github/scripts/otel-naming/**
             .github/scripts/rename/**
             .github/workflows/reusable-check-levelization.yml
+            .github/workflows/reusable-check-otel-naming.yml
             .github/workflows/reusable-check-rename.yml
             .github/workflows/on-pr.yml
 
@@ -108,6 +110,11 @@ jobs:
     if: ${{ needs.should-run.outputs.go == 'true' }}
     uses: ./.github/workflows/reusable-check-levelization.yml
 
+  check-otel-naming:
+    needs: should-run
+    if: ${{ needs.should-run.outputs.go == 'true' }}
+    uses: ./.github/workflows/reusable-check-otel-naming.yml
+
   check-rename:
     needs: should-run
     if: ${{ needs.should-run.outputs.go == 'true' }}
@@ -176,6 +183,7 @@ jobs:
     if: failure() || cancelled()
     needs:
       - check-levelization
+      - check-otel-naming
       - check-rename
       - clang-tidy
       - build-test

.github/workflows/reusable-check-otel-naming.yml

@@ -0,0 +1,28 @@
+# This workflow checks that OpenTelemetry span-attribute names stay consistent
+# across the code (*SpanNames.h), collector, Tempo, dashboards, and docs.
+# See .github/scripts/otel-naming/check_otel_naming.py and the
+# "Telemetry span attribute naming" section in CONTRIBUTING.md.
+name: Check OTel naming
+
+# This workflow can only be triggered by other workflows.
+on: workflow_call
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}-otel-naming
+  cancel-in-progress: true
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  otel-naming:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+      - name: Check OTel naming
+        # The script is stdlib-only and reads only files already in the tree;
+        # it enforces each rule only when the layer it needs is present, so it
+        # works whether telemetry changes land in one PR or several.
+        run: python .github/scripts/otel-naming/check_otel_naming.py