feat(core): session-scoped dock UI state — restore open/selected dock, tab, and scroll across reloads - #527

…, tab, and scroll across reloads

Splits the dock panel's persisted state in two: config (geometry/position/
mode/inactiveTimeout) stays in localStorage (vite-devtools-dock-state,
cross-tab), while *state* (open, selected dock, active tab, scroll position)
moves to sessionStorage (vite-devtools-dock-session, per-tab) — a full page
reload no longer leaves the panel open-but-empty or resets scroll/tab.

- createDocksContext (context.ts) now backs open + selectedId with a single
  useSessionStorage store, merged with the geometry-only panelStore into the
  same DockPanelStorage shape every dock component already reads/writes
  through context.panel.store — only open's backing store changes.
- A restored selectedId is validated once at boot (once dock entries have
  actually loaded) against being a real selectable leaf — not a group, a
  subTabs anchor, or a stale id — clearing it without routing through
  switchEntry (which would force the panel back open). Past that one-time
  check, switchEntry may legitimately land on a group/anchor id itself (e.g.
  a subTabs anchor with no live member yet) — this doesn't re-litigate that.
- DockEmbedded now mirrors DockStandalone's own auto-select-first-entry
  boot guard, gated on the panel actually being open.
- ViewJsonRender provides its dock entry id for descendants to inject, and
  restores/persists its own scroll position per dock, debounced.
- New useUncontrolledValue composable: session-persisted fallback for a
  json-render element's own uncontrolled value, keyed by the injected dock
  id plus a signature of the element's static shape (works around
  FlatElement.key not being forwarded to registry components). Tabs now
  uses it instead of its hand-rolled ref; Select/TextInput/Switch — until
  now inert while unbound — get it too.

Two behavior changes ship with this, both intentional:
- Opening the docks in one tab no longer auto-opens them in another tab of
  the same page (open moved from localStorage to sessionStorage).
- The very first load after this ships, the panel starts closed even if a
  user's old vite-devtools-dock-state said open: true — that key's open is
  simply never read again.

🤖 Generated with [Claude Code](https://claude.com/claude-code)