[BUG] Title-bar commands act on the wrong provider instance when sidebar and editor tab coexist

[easonLiangWorldedtech]

Tracking series: vps2 durable per-view state — easonLiangWorldedtech#41 (fix unit F0).
Fix: draft PR #1528 (this issue is the issue of record for that PR, created at PR-open time).

Summary

With the Zoo Code sidebar and an "Open in editor" tab open at the same time, the title-bar commands (+ / Settings / History / Marketplace / popout / focus input) do not reliably act on the instance the user clicked. The commands are wired to a single surface-blind "visible" provider, and the panel bookkeeping mutates shared slots.

Repro

1. Open the Zoo Code sidebar; start a task.
2. Open a second Zoo Code view via "Open in editor" (or the popout command). A new ClineProvider + WebviewPanel is created.
3. Click the title-bar buttons (Settings / History / Marketplace / +) on the sidebar and on the editor tab title bars.

Symptoms (verified at upstream/main 0d937c0)

• Mutual panel wipe: setPanel writes null into the other panel slot on every resolve (and the sidebar's onDidDispose never clears its slot) — the sidebar/tab slot references drift out of sync as the two views coexist.
• No tab reuse: every "Open in editor" creates a fresh provider + panel even when a live tracked tab already exists.
• Surface-blind targeting: the five title-bar commands are contributed to both view/title and editor/title, yet all of them resolve the target via the insertion-order "last visible" provider — so a click on the tab's title bar can execute against the sidebar instance (or vice versa), posting settings/history/marketplace/plus actions to the wrong webview.
• focusPanel: resolves tab-first from the same drifted slots (self-corrects once the wipe is fixed).

Impact

User actions land in the wrong view instance: a Settings click on the tab can open settings on the sidebar, a + on the tab can evict the sidebar's task, and focus commands target the wrong surface. State written by those actions is attributed to the wrong view.

Fix (PR #1528)

• no-wipe setPanel (each slot owns its assignment);
• sidebar title-bar handlers target the click-origin provider;
• four new *InTab command ids rewire the editor/title menu; tab handlers resolve the owning instance via the new ClineProvider.getInstanceForView(panel);
• openClineInNewTab reuses the live tracked tab panel;
• focusInput post condition narrowed to sidebarPanel && !tabPanel.
  Known limitation documented in the PR: zoo-code.newTask (command palette) stays on the visible-provider path (focus-sidebar fallback).