Fix 5 CodeRabbit findings on PR #14789 (BOLT-1951 specs docs)

PR #14789 BOLT-1951/specs, docs-only. 5 CodeRabbit CHANGES_REQUESTED findings, all markdown consistency: 1. sftp-poll-handler/spec.md L98/L245: replace datalake-bucket/prefix wording with destBucket/destPrefix. 2. phase1-audit.md L23: scope generic device.detected MeterState branch to NISC-only. 3. meter-devices-from-telemetry-sources/design.md L34: resolve backfill create-vs-link contradiction (link-only, no creates). 4. sonnen notes.md L53: change telemetry-only to telemetry always + optional device.detected when configured. 5. smt-ingest-meter-devices/spec.md L81: retry semantics - device provisioning independently retryable / idempotent, not whole-file republish.