fix(native): meet DSH 0.1.6-alpha.2 guide-id and turn-tail contracts

DSH 0.1.6-alpha.2 made two plugin-facing contracts stricter, and both broke
this plugin silently:

- `SidebarRightGuideEntry.id` is now required and unique per provider. The
  native tab registrations sent guide entries without one, so the second kind
  collided on `undefined` and `SidebarRightTabRegistry.register` threw
  'duplicate guide entry id'. The throw happens inside `ctx.inject`'s callback
  body, which cordis swallows, so the whole native surface stayed empty with no
  symptom beyond a missing guide row.
- `conversation.chat.turnTail` changed from a `chain` to an additive `list`.
  The chain's `select` made one entry render and let this plugin REPLACE the
  host's produced-files row; a list cannot express that, and the registration
  now throws 'list slot ... requires options.id'. Upstream chose the list
  deliberately ('An additive list lets both plugins contribute without either
  knowing the other's data or rendering'), so the plugin's row can only ever
  duplicate the host's deliverables row -- which itself opens files through the
  host's openFile, i.e. into this plugin's editor. The contribution is removed
  and the row is the host's alone.

The file-opening half survives as `sidebar-file.ts` (the changes tab and the
editor host still use it), and `resolveSidebarPath` moves to the `paths.ts`
path-helper module beside its siblings. `registerNativeSurface` grows an
optional `reportFailure` so a future contract break reaches the visible
diagnostic strip instead of a silently empty guide, and one bad descriptor can
no longer take the remaining registrations down with it.

src/client/changes/DiffPane.tsx

@@ -14,7 +14,7 @@ import type { SessionScope } from '../api.ts'
 import { api, htmlUrl } from '../api.ts'
 import { t } from '../locales.ts'
 import { baseName } from '../paths.ts'
-import { resolveSidebarPath } from '../produced-files.ts'
+import { resolveSidebarPath } from '../paths.ts'
 import { HTML_IFRAME_SANDBOX } from '../html-preview.ts'
 import type { SidebarDiffRef, SidebarTab } from '../state.ts'
 import { DiffRows, ReadRows } from '../diff/DiffRows.tsx'

src/client/changes/GitLens.tsx

@@ -19,7 +19,7 @@ import type { GitLogEntry, GitStatusEntry, GitStatusResult, GitWorktree, Session
 import { api } from '../api.ts'
 import { usePolling } from '../use-polling.ts'
 import { baseName, isWithinWorkspace, relativeTo } from '../paths.ts'
-import { resolveSidebarPath } from '../produced-files.ts'
+import { resolveSidebarPath } from '../paths.ts'
 import { relativeTime, t } from '../locales.ts'
 import type { SidebarDiffRef, SidebarStore } from '../state.ts'
 import css from './changes.module.css'