Refactor code structure for improved readability and maintainability; removed redundant code blocks and optimized function calls.

ops/mongo/indices/README.md

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+# MongoDB Provenance Indexes
+
+Indexes supporting Sprint 401 reachability/provenance queries.
+
+## Available indexes
+- `events_by_subject_kind_provenance`: `(subject.digest.sha256, kind, provenance.dsse.rekor.logIndex)` for subject/kind lookups with Rekor presence.
+- `events_unproven_by_kind`: `(kind, trust.verified, provenance.dsse.rekor.logIndex)` to find unverified or missing-Rekor events per kind.
+- `events_by_rekor_logindex`: `(provenance.dsse.rekor.logIndex)` to audit Rekor alignment.
+
+## Apply
+```js
+// From mongo shell (connected to provenance database)
+load('ops/mongo/indices/events_provenance_indices.js');
+```
+
+Indexes are idempotent; rerunning is safe.