Port feature from vitejs/devtools#525: mirror the dock panel's localStorage state into shared state

[antfubot]

Context

vitejs/devtools#525 ("feat(core): mirror the dock panel's localStorage state into shared state") by @dvcolomban made the dock panel's browser-local panelStore (vite-devtools-dock-state) visible to Node-side plugins by mirroring it into rpc.sharedState under the same key, via a new useLocalStorageSharedState helper. It touched packages/core/src/client/inject/runtime.ts in vitejs/devtools, which moved here as part of the v0.9 migration — the equivalent bootstrap today is packages/hub-ui/src/client/embedded/index.ts, and the panelStore/DEFAULT_DOCK_PANEL_STORE it wraps now lives in packages/hub-ui/src/client/state/docks.ts.

Original PR description

Why

panelStore (the vite-devtools-dock-state key) is purely browser-local today — nothing on the Node/server side can see it, including whether the panel is even open. Any Node-side plugin that wants to react to dock UI state — gate some behavior on visibility, log usage, sync it elsewhere — has nothing to observe.

What changed

• Wraps the existing useLocalStorage call with a small generic helper, useLocalStorageSharedState, that mirrors the whole value into rpc.sharedState under the same key. Shared-state mutations already round-trip through the server before reappearing locally, so that's the entire mechanism — no new dock-entry field, no client-script gating, no RPC command, no trust handshake.
• Mirrors the whole object rather than cherry-picking open: it's already one useLocalStorage-backed, fully serializable, browser-local singleton (not per-tab), so a second, narrower key for just one field would just be a redundant place for that field to live.

Known limitation, flagging it rather than hiding it: shared state is one authoritative value, last-mutation-wins — with two tabs open, a Node-side consumer watching e.g. open sees whichever tab mutated most recently. Per-connection keying would need a way to garbage-collect a disconnected tab's entry, and nothing in the public API exposes that today, so I went with the simpler singleton.

Diff: https://github.com/vitejs/devtools/pull/525/files

For agents picking this up

• Read the diff at feat(core): mirror the dock panel's localStorage state into shared state vitejs/devtools#525 for the useLocalStorageSharedState helper implementation and its known-limitation note (last-mutation-wins across tabs).
• Port the helper and its use over panelStore/DEFAULT_DOCK_PANEL_STORE to packages/hub-ui/src/client/state/docks.ts (and wherever the useLocalStorage call is wired today), adapting to whatever has shifted since the fork. This is a good candidate for a framework-neutral home if other devframe UIs would benefit, but keep it local to hub-ui unless that's an easy lift.
• Note feat(core): session-scoped dock UI state — restore open/selected dock, tab, and scroll across reloads vitejs/devtools#527 ("session-scoped dock UI state") folds a selectedId field into the same panelStore object — check whether that PR's port (tracked separately) landed first so this shared-state mirror covers the merged shape rather than a stale one.
• Credit @dvcolomban as the original author: include a Co-authored-by: dvcolomban <...> trailer (look up their GitHub noreply email, or omit if unavailable) and mention them in the PR description.
• Link back to feat(core): mirror the dock panel's localStorage state into shared state vitejs/devtools#525 in the PR description.
• Close this issue when the port merges.