ui: the platform shells take the Harmonia 3 reference layout the generated shell has (#7428)

[delchev]

Cause

#7400 moved the generated application shell to the Harmonia 3 reference layout and made it drop its own gutter and card chrome in embedded mode on purpose: the host owns the frame. The host never drew it. The platform shells still carried the 1.x structure - an x-h-split with a permanently locked, gutterless sidebar panel, --sidebar-width: 100% to fill it, a plain toolbar, the hosted iframe in a bare flex div - so the same form looked like the old stack inside the application shell and like the reference in its own.

Change

The six sidebar shells (application, personal, partner, admin, monitoring, database) now share the generated shell's structure:

• bg-sidebar body; the ONE sidebar element in a plain shrink-0 flex slot as a direct peer, moved into the x-h-sheet drawer below 1024px; x-h-sidebar / header / footer data-borderless.
• Content column min-w-0 flex-1 overflow-hidden with a p-2 gutter around a rounded-xl border shadow-sm <main> card, both dropped when narrow through a :class binding. The hosted iframe sits inside the card, so an embedded app inherits the frame it deliberately does not draw.
• Brand row as x-h-sidebar-header-item (the projection product-switcher stays), the sidebar content as the <nav> landmark, the logged-in user as the initials x-h-avatar with x-h-menu-label in place of the presentational li + tile (id="user-menu-trigger" kept), a route-loading x-h-progress bar.
• Each shell's own js/appShell.js: hiddenPanels.left -> isSmallScreen, isOpen -> showSidebarSheet, $refs.sidebarPanel/overlay -> sidebarSlot/sidebarSheet, routeLoading off pinecone:start / :end / :fetch-error, the refreshIcons no-op removed with its call sites. These are per-shell copies loaded only by their own page, so unlike the shared runtime (ui: the shared shell runtime dropped the names every already-generated app shell binds - embedded apps show their own sidebar (#7400) #7427) they carry no cross-vintage contract.

The builder shell is deliberately untouched: it has no sidebar, and its x-h-split is the resizable chat/canvas pane - the one use Split is for. Every stable id the ITs pin (monitoring-*, user-menu-trigger, #app, the iframe) is unchanged.

Verification

• HarmoniaContractIT green: every x-h-* directive and utility class of the six pages checked against the pinned 3.1.2 webjar.
• PerspectiveGroupAggregationIT, ShellSwitcherIT, MonitoringShellIT, DatabaseShellIT green headless (the first run had two Chrome session/renderer errors while a second IT run drove Chrome on the same machine; both classes passed in full on rerun).
• mvn -T 1C formatter:validate with the cache wiped.
• Not verified: a real browser look at 1440px / 900px, and an embedded generated app inside the new frame - please eyeball once before merging.

Fixes #7428

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