fix(dashboard): keep the logs ← home link + sub-tabs on one row

The /logs.html header puts a flex:1 sub-tab strip (`.logs-tabbar`) next
to the ← home back-link inside the flex `.page-header`. The strip is
itself a flex container, so its default `min-width: auto` keeps it at its
intrinsic content width and — without an explicit nowrap on the parent —
it gets pushed onto its own row under the back-link.

Mirror the working dashboard chrome (`.dashboard-chrome` / `.tabbar`,
which sets `flex-wrap: nowrap`): make `.page-header` explicitly nowrap and
give `.logs-tabbar` `min-width: 0` so it shrinks to share the row instead
of wrapping. Affects every standalone page that uses `.page-header`
(flow / logs / stats / settings); the nowrap is correct for all of them.

frontend/packages/shared/src/chrome.css

@@ -23,6 +23,12 @@
   backdrop-filter: blur(8px) saturate(120%);
   border-bottom: 1px solid var(--purple-dim);
   display: flex;
+  /* Keep the back-link + sub-tab nav on one row. Without an explicit
+     nowrap a flex:1 sub-tab strip (e.g. /logs.html's `.logs-tabbar`)
+     whose intrinsic min-content width can't shrink (default
+     `min-width: auto`) gets pushed onto its own line. The strip pairs
+     this with `min-width: 0` so it can shrink instead of wrapping. */
+  flex-wrap: nowrap;
   align-items: center;
   gap: 1.5em;
   padding: 0.5em 1.5em;