chore(compat/loki): drop 4 stale detected_level should_skip entries

[tsouza]

Summary

The 4 detected_level entries in compatibility/loki/cerberus-test-queries.yml
carried a "harness seed-gap" rationale claiming the seeder doesn't push
structured-metadata input for the reference Loki to index. That rationale
was stale. PR #412 wired structured-metadata into the seeder via
pushLoki's logproto.LabelAdapter block in compatibility/loki/cmd/seed/main.go
(every entry now carries StructuredMetadata: [{Name: "detected_level", Value: <lvl>}]),
and loki-config.yaml already has allow_structured_metadata: true.

PR #712 (which empties the entire should_skip block) ran on top of these
entries' removal and reported diff: "" against the reference Loki for all
four — verified independently from the artifact:

• regression/structured-metadata.yaml#Combined line and metadata filter
• regression/structured-metadata.yaml#Drilldown with failed search and error level
• regression/structured-metadata.yaml#Drilldown with error/warn level and refused search
• exhaustive/aggregations.yaml#Count aggregated by detected_level

Dropping these 4 entries promotes them out of the overlay back into the
compat denominator with verified reference baselines. The closure is a
documentation/overlay cleanup, not a seeder change — the seeder code
path was already correct, just the rationale was stale.

The remaining 20 entries stay as-is:

• Upstream-pinned skip: true rows (numeric label filters / stddev_over_time /
  quantile_over_time not supported by Loki's v2 engine).
• Plain seed-gap entries on pod / namespace / service_name / cluster /
  container labels (separate cluster; tracked separately).

Test plan

• CI compatibility/loki green — the 4 lifted entries now contribute
  parity baselines to the score.
• CI check / lint green — YAML-only change, no Go code touched.

🤖 Generated with Claude Code