fix(plugin-redis): Cluster over SSH fails with wrong advice and typed SCAN drops its cursor

[datlechin]

Summary

• Redis Cluster through a tunnel (SSH, Cloudflare, SOCKS, Tunnel Command or Cloud SQL Proxy) failed to connect with advice to set Connection Mode to Cluster. Root cause: every tunnel rewrites a Redis connection to Standalone against the first host, and RedisTopologyDiagnostics.mismatch only honored isTunneled for a Sentinel node, so a cluster data node fell through to the "set Connection Mode to Cluster" refusal the user could never satisfy.
• A SCAN typed in a query tab showed one page of keys with no way to continue, and an empty mid-scan page showed only "No rows". Root cause: buildScanPageResult never read page.cursor, so the next cursor from the SCAN reply was dropped before the result reached the status bar.

The unfinished page is deliberately not marked truncated: isTruncated shows Fetch All, which re-runs the same SCAN <cursor> text and would return the same page. The cursor goes out as the result's status message instead, and a cluster cursor is shown whole (<node id>-<cursor>) so it can be passed back to SCAN.

Tests

• RedisTopologyDiagnosticsTests/clusterThroughTunnelIsFine: spec change, now passes actual: .cluster (the old version passed .standalone and never tested the cluster case). Fails without the fix.
• RedisTopologyDiagnosticsTests/standaloneThroughTunnelIsFine: new, keeps the case the old test covered.
• RedisKeyspacePageTests (new, 9 cases): unfinishedPageNamesNextCursor, finishedPageHasNoNotice, emptyUnfinishedPageNamesNextCursor, clusterCursorIsNamedWhole, and the RedisScanPageOutcome cases unfinishedPageOutcomeCarriesCursorWithoutTruncating, emptyUnfinishedPageOutcomeCarriesCursor, finishedPageOutcomeHasNoStatusMessage, pageOverRowLimitIsCappedAndTruncated, incompletePageIsTruncated. They fail without the fix: the target does not compile, because nothing on the page carries the cursor.
• 12 Redis suites, 79 cases, all passing.

Docs

The docs rewrite branch covers the user-facing text for both changes.