chore(sync): re-base the fork onto upstream dsh-better-sidebar v0.19.1

The fork was pinned at upstream v0.18.0. That is the entire reason the window
ran TWO sidebars and TWO near-identical panel toggles: DSH 2.0.10 ships its own
right sidebar (@deepseek-ai/dsh-client-ui-sidebar-right), and upstream only
adopted it in v0.19.0-alpha.1 — which arrived after our fork point. v0.19.1 is
also the one upstream line whose support range actually matches our host
(engines.dsh >=0.1.5-rc.1, 14 DSH peers ^0.1.5-rc.1, host = 0.1.5-rc.2), so it
is the only tag the host's startup precheck accepts.

What upstream v0.18.0 → v0.19.1 brings
- src/client/native/{index,surface,tab-adapter}.tsx: every tab the plugin can
  draw becomes an OFFICIAL native tab type + body, and an external plugin's
  descriptor registered later gets its native type too. This is what retires
  the fork's own right panel — and with it the duplicate toggle cluster
  (`toggleCluster` is gone from v0.19.1).
- native tab-chip icons via the `sidebar.right.pane.tab.title` seat, coloured
  built-in tab icons, file/folder glyphs from DSH's own `FileTypeIcon`.
- guide descriptions (DSH renders them while the guide lists <= 4 entries),
  tab bodies that fill the panel, and the 0.1.5-rc.2 adaptation work we were
  carrying by hand (peer/devDep pinning, primitives' transitive devDeps).

How the sync was done
Rebuilt the tree from the v0.19.1 tag rather than resolving 53 conflicted
files: our v0.18.0 delta was measured first and is only (a) one mechanical
rename `dsh-better-sidebar` -> `dsh-apes-sidebar` and (b) ten real edits. So:
tag tree + rename (scoped: code/config/scripts/tests/README, while the 46
historical docs/plans records and switch.sh's upstream package name stay
untouched) + re-applied deltas + our apes module.

Fork deltas re-applied on the new base
- src/client/apes/ (icons / locales / tabs): the three apes:* information-layer
  tabs (agents / apps / profile), registered through the same BetterSidebarService
  as the builtins — which is exactly why they now ride upstream's native adapter
  into the official sidebar for free.
- identity: package.json (name/version 1.2.0/description/forkedFrom), dsh.plugin.json
  (id/version), SIDEBAR_SERVICE_VERSION 1.2.0, README fork notice,
  docs/external-plugin-guide.md.
- scripts/switch.sh + the pnpm switch* scripts (apes <-> upstream two-line switch).
- tests/apes-tabs.spec.ts (unescaped: it starts from the v0.19.1 base).

Dropped
- the Phase A native-registration spike (`apes/native-tabs.tsx` + its spec): it
  re-derived by hand exactly what upstream's native layer already does — the
  hand-written bridge is dead weight now, and v0.19.1's own e2e/jsdom lanes
  cover the same seat contract far better.
- the unused apesProfileGuideDesc key and the two package.json.bak.* backups.

Verified on the new base: typecheck clean; build clean; 1351 passed / 9 skipped
(128 files), up from 1255 on the old base.

tests/e2e/perf.e2e.ts

@@ -5,7 +5,7 @@
  * It exists to put NUMBERS on the sidebar's client-side cost in a real
  * mounted `dsh web` (the same scratch-profile boot as scripts/e2e-mount.sh):
  *
- *   1. mount latency  — navigationStart → `[data-dsh-better-sidebar]`
+ *   1. mount latency  — navigationStart → `[data-dsh-apes-sidebar]`
  *      attached, sampled by an init-script probe (rAF loop, so it catches
  *      the attach even before Playwright's first poll);
  *   2. longtasks      — every >50ms main-thread task from first paint
@@ -63,7 +63,7 @@ const PERF_PROBE = `(() => {
     for (const entry of list.getEntries()) perf.longtasks.push({ start: entry.startTime, duration: entry.duration })
   }).observe({ entryTypes: ['longtask'] })
   const check = () => {
-    if (document.querySelector('[data-dsh-better-sidebar]') !== null) { perf.mountAt = performance.now(); return }
+    if (document.querySelector('[data-dsh-apes-sidebar]') !== null) { perf.mountAt = performance.now(); return }
     requestAnimationFrame(check)
   }
   requestAnimationFrame(check)
@@ -114,7 +114,7 @@ test('measure: mount latency, longtasks and bundle cost through a full tab sweep
   await page.addInitScript(PERF_PROBE)
   await page.goto(PAGE_URL, { waitUntil: 'domcontentloaded' })
   await expect(page.locator('#root > *')).not.toHaveCount(0, { timeout: 90_000 })
-  const sidebar = page.locator('[data-dsh-better-sidebar]')
+  const sidebar = page.locator('[data-dsh-apes-sidebar]')
   await expect(sidebar).toBeAttached({ timeout: 90_000 })
 
   const mountLatency = await page.evaluate(() =>
@@ -183,7 +183,7 @@ test('measure: bottom-strip drag frame pacing', async ({ page }) => {
   await page.addInitScript(PERF_PROBE)
   await page.goto(PAGE_URL, { waitUntil: 'domcontentloaded' })
   await expect(page.locator('#root > *')).not.toHaveCount(0, { timeout: 90_000 })
-  const sidebar = page.locator('[data-dsh-better-sidebar]')
+  const sidebar = page.locator('[data-dsh-apes-sidebar]')
   await expect(sidebar).toBeAttached({ timeout: 90_000 })
   await dismissOnboarding(page)
 
@@ -227,7 +227,7 @@ test('measure: bottom-strip drag frame pacing', async ({ page }) => {
   await expect
     .poll(async () => {
       const probe = await page.evaluate(() => {
-        const bottom = document.querySelector('[data-dsh-better-sidebar] [data-dsh-bottom-panel]')
+        const bottom = document.querySelector('[data-dsh-apes-sidebar] [data-dsh-bottom-panel]')
         if (bottom === null) return null
         const strip = [...bottom.querySelectorAll<HTMLElement>('*')].find(el => getComputedStyle(el).cursor === 'row-resize')
         if (strip === undefined) return null
@@ -239,7 +239,7 @@ test('measure: bottom-strip drag frame pacing', async ({ page }) => {
     }, { timeout: 30_000 })
     .toBeLessThanOrEqual(8)
   const stripPoint = await page.evaluate(() => {
-    const bottom = document.querySelector('[data-dsh-better-sidebar] [data-dsh-bottom-panel]')
+    const bottom = document.querySelector('[data-dsh-apes-sidebar] [data-dsh-bottom-panel]')
     if (bottom === null) return null
     const strip = [...bottom.querySelectorAll<HTMLElement>('*')].find(el => getComputedStyle(el).cursor === 'row-resize')
     if (strip === undefined) return null