fix(worktrees): a host-scoped purge leaves a surviving twin's tabs and edits alone (#30030)

src/shared/worktree/host-qualified-identity.test.ts

@@ -5,7 +5,9 @@ import {
   getExecutionHostIdFromWorktreeHostIdentity,
   getWorktreeHostIdentity,
   getWorktreeIdFromHostIdentity,
-  type HostScopedWorktreeKey
+  hostWorktreeTarget,
+  type HostScopedWorktreeKey,
+  type HostWorktreeTarget
 } from './host-qualified-identity'
 
 const WORKTREE_ID = 'repo-1::/work/orca'
@@ -120,3 +122,18 @@ describe('worktree host identity golden bytes', () => {
     expect([raw, forged]).toEqual([key, WORKTREE_ID])
   })
 })
+
+describe('host worktree target', () => {
+  it('carries the row id and its concrete host', () => {
+    const target = hostWorktreeTarget({ id: WORKTREE_ID, hostId: toSshExecutionHostId('box') })
+    expect(target).toEqual({ hostId: 'ssh:box', worktreeId: WORKTREE_ID })
+  })
+
+  it('cannot be forged from a plain object or built without a host', () => {
+    // @ts-expect-error only hostWorktreeTarget mints the brand
+    const forged: HostWorktreeTarget = { hostId: 'local', worktreeId: WORKTREE_ID }
+    // @ts-expect-error an unqualified row has no host to scope to
+    hostWorktreeTarget({ id: WORKTREE_ID, hostId: undefined })
+    expect(forged.worktreeId).toBe(WORKTREE_ID)
+  })
+})

src/shared/worktree/host-qualified-identity.ts

@@ -22,6 +22,23 @@ declare const hostScopedWorktreeKeyBrand: unique symbol
 // Why: for new code only; existing raw-id stores stay as they are (D7).
 export type HostScopedWorktreeKey = string & { readonly [hostScopedWorktreeKeyBrand]: true }
 
+declare const hostWorktreeTargetBrand: unique symbol
+
+/** One host's copy of a workspace, for destructive entry points that must not reach its twin. */
+export type HostWorktreeTarget = {
+  readonly hostId: ExecutionHostId
+  readonly worktreeId: string
+  readonly [hostWorktreeTargetBrand]: true
+}
+
+export function hostWorktreeTarget(row: {
+  id: string
+  hostId: ExecutionHostId
+}): HostWorktreeTarget {
+  // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: the only constructor of the brand; `hostId` is a concrete host by the parameter type.
+  return { hostId: row.hostId, worktreeId: row.id } as HostWorktreeTarget
+}
+
 /**
  * Stable key for one workspace on one host (STA-4343).
  *