chore: split patterns out from OTTL skills

CLAUDE.md

@@ -33,6 +33,11 @@ These two skills have a strict boundary: **application code vs Collector configu
 When content could live in either skill, apply this rule: if the guidance tells an agent how to modify **application code or deployment specs**, it belongs in `otel-instrumentation`; if it tells an agent how to modify **Collector YAML configuration or Collector deployment manifests**, it belongs in `otel-collector`.
 Cross-reference the other skill for context, but do not duplicate Collector configuration in `otel-instrumentation` or SDK/pod-spec configuration in `otel-collector`.
 
+## Keeping SKILL.md index lists in sync with rule files
+
+Some `SKILL.md` files contain a bullet list that mirrors the `##` headings in a referenced rule file (marked with a `<!-- keep-in-sync -->` comment).
+When adding, removing, or renaming a `##` heading in the rule file, update the corresponding list in `SKILL.md` so the entries match one-to-one.
+
 ## Prose rules
 
 Follow these rules when writing or editing prose in this project.

skills/otel-ottl/SKILL.md

@@ -101,85 +101,17 @@ service:
 
 ## Common patterns
 
-### Set attributes
-
-```
-set(resource.attributes["k8s.cluster.name"], "prod-aws-us-west-2")
-```
-
-### Redact sensitive data
-
-See [redaction](./rules/redaction.md) for strategies (replace, mask, hash, delete, drop) with examples.
-
-### Drop telemetry by pattern
-
-```
-IsMatch(metric.name, "^k8s\\.replicaset\\..*$")
-```
-
-### Drop stale data
-
-```
-time_unix_nano < UnixNano(Now()) - 21600000000000
-```
-
-### Backfill missing timestamps
-
-```yaml
-processors:
-  transform:
-    log_statements:
-      - context: log
-        statements:
-          - set(log.observed_time, Now()) where log.observed_time_unix_nano == 0
-          - set(log.time, log.observed_time) where log.time_unix_nano == 0
-```
-
-### Filter processor example
-
-```yaml
-processors:
-  filter:
-    metrics:
-      datapoint:
-        - 'IsMatch(ConvertCase(String(metric.name), "lower"), "^k8s\\.replicaset\\.")'
-
-service:
-  pipelines:
-    metrics:
-      receivers: [otlp]
-      processors: [filter, batch]
-      exporters: [debug]
-```
-
-### Transform processor example
-
-```yaml
-processors:
-  transform:
-    trace_statements:
-      - context: span
-        statements:
-          - set(span.status.code, STATUS_CODE_ERROR) where span.attributes["http.response.status_code"] >= 500
-          - set(span.attributes["env"], "production") where resource.attributes["deployment.environment"] == "prod"
-
-service:
-  pipelines:
-    traces:
-      receivers: [otlp]
-      processors: [transform, batch]
-      exporters: [debug]
-```
-
-### Defensive nil checks
-
-```
-resource.attributes["service.namespace"] != nil
-and
-IsMatch(ConvertCase(String(resource.attributes["service.namespace"]), "lower"), "^platform.*$")
-```
-
-See [cardinality](./rules/cardinality.md) for normalizing high-cardinality attributes (path segments, IP masking, attribute count/length limits) and [enrichment](./rules/enrichment.md) for adding static resource attributes.
+<!-- keep-in-sync: each entry must match a ## heading in ./rules/patterns.md -->
+- [Set attributes](./rules/patterns.md#set-attributes)
+- [Drop telemetry by pattern](./rules/patterns.md#drop-telemetry-by-pattern)
+- [Drop stale data](./rules/patterns.md#drop-stale-data)
+- [Backfill missing timestamps](./rules/patterns.md#backfill-missing-timestamps)
+- [Filter processor example](./rules/patterns.md#filter-processor-example)
+- [Transform processor example](./rules/patterns.md#transform-processor-example)
+- [Defensive nil checks](./rules/patterns.md#defensive-nil-checks)
+- [Redact sensitive data](./rules/redaction.md) — strategies: replace, mask, hash, delete, and drop.
+- [Normalize high-cardinality attributes](./rules/cardinality.md) — path segments, IP masking, and attribute count/length limits.
+- [Enrich telemetry with static attributes](./rules/enrichment.md)
 
 ## Error handling
 

skills/otel-ottl/rules/patterns.md

@@ -0,0 +1,75 @@
+# Common OTTL patterns
+
+## Set attributes
+
+```
+set(resource.attributes["k8s.cluster.name"], "prod-aws-us-west-2")
+```
+
+## Drop telemetry by pattern
+
+```
+IsMatch(metric.name, "^k8s\\.replicaset\\..*$")
+```
+
+## Drop stale data
+
+```
+time_unix_nano < UnixNano(Now()) - 21600000000000
+```
+
+## Backfill missing timestamps
+
+```yaml
+processors:
+  transform:
+    log_statements:
+      - context: log
+        statements:
+          - set(log.observed_time, Now()) where log.observed_time_unix_nano == 0
+          - set(log.time, log.observed_time) where log.time_unix_nano == 0
+```
+
+## Filter processor example
+
+```yaml
+processors:
+  filter:
+    metrics:
+      datapoint:
+        - 'IsMatch(ConvertCase(String(metric.name), "lower"), "^k8s\\.replicaset\\.")'
+
+service:
+  pipelines:
+    metrics:
+      receivers: [otlp]
+      processors: [filter, batch]
+      exporters: [debug]
+```
+
+## Transform processor example
+
+```yaml
+processors:
+  transform:
+    trace_statements:
+      - context: span
+        statements:
+          - set(span.status.code, STATUS_CODE_ERROR) where span.attributes["http.response.status_code"] >= 500
+          - set(span.attributes["env"], "production") where resource.attributes["deployment.environment"] == "prod"
+
+service:
+  pipelines:
+    traces:
+      receivers: [otlp]
+      processors: [transform, batch]
+      exporters: [debug]
+```
+
+## Defensive nil checks
+
+```
+resource.attributes["service.namespace"] != nil
+and
+IsMatch(ConvertCase(String(resource.attributes["service.namespace"]), "lower"), "^platform.*$")
+```