Fix flaky test [chromium] _ e2e/nodes-roster-width.spec.ts:400:5 _ nodes on a phone _ host page State fact, one bar box, Shared hosting rhythm and the Hosts row_s age at 448px _premerge

The merge lane saw `[chromium] _ e2e/nodes-roster-width.spec.ts:400:5 _ nodes on a phone _ host page State fact, one bar box, Shared hosting rhythm and the Hosts row_s age at 448px _premerge` fail and then pass on a rerun of the same tree. - Test: `[chromium] _ e2e/nodes-roster-width.spec.ts:400:5 _ nodes on a phone _ host page State fact, one bar box, Shared hosting rhythm and the Hosts row_s age at 448px _premerge` - Tree: `d47c731a45f4208a3a5202b340503f720b3efd66` - Lane task: 9223 - Flake record: 01a166db-222f-76cf-9af2-8db33fc7c3e3 Make it deterministic; do not delete it unless it tests nothing.

Made the 448px host-page test deterministic: the Shared hosting heading and checkbox are now read in one frame and polled, not as two boundingBox reads a reflow could straddle. 20/20 repeat runs and quick gate green; PR #6710 queued to the merge lane. Memory: none applied.