fix(worktree): skip retirement backfill on every non-local host (#15023)

The backfill guard tested repo.connectionId, but a runtime-owned repo
carries executionHostId with no connectionId, so it read as local. The
scan then walked this machine's workspace and agent-transcript
directories and filed the result under the runtime host's namespace —
retiring names never used there while missing the ones that were.

Guard on the execution host id instead. Ongoing retirement was already
correct for these repos; only the one-time historical seed was wrong.

src/main/worktree-name-retirement.test.ts

@@ -336,4 +336,60 @@ describe('ensureRetiredWorktreeNamesBackfilled', () => {
 
     expect(merged).toEqual([])
   })
+
+  it('skips a runtime-owned repo, which has no connectionId but is still not local', async () => {
+    // Why: a `connectionId` check calls this repo local, so the scan reads THIS machine's
+    // directories and files them under the runtime's namespace — retiring names never used there
+    // while missing the ones that were. The host id is the only reliable local test.
+    const root = await mkdtemp(join(tmpdir(), 'orca-retirement-runtime-'))
+    const workspaceRoot = join(root, 'workspaces')
+    await mkdir(join(workspaceRoot, FIRST), { recursive: true })
+    const merged: string[] = []
+    const store = {
+      mergeRetiredWorktreeNames: (_repoId: string, names: Iterable<string>) => {
+        merged.push(...names)
+        return true
+      }
+    }
+    const runtimeRepo = {
+      ...makeRepo('repo-runtime', '/repos/runtime'),
+      executionHostId: 'runtime:env-1'
+    } as Repo
+
+    try {
+      const collisionKey = await ensureRetiredWorktreeNamesBackfilled(store, runtimeRepo, {
+        workspaceDir: workspaceRoot,
+        nestWorkspaces: false
+      })
+
+      expect(merged).toEqual([])
+      expect(collisionKey).toBeNull()
+    } finally {
+      await rm(root, { force: true, recursive: true })
+    }
+  })
+
+  it('still backfills a plain local repo, so the skip is scoped to non-local hosts', async () => {
+    const root = await mkdtemp(join(tmpdir(), 'orca-retirement-local-'))
+    const workspaceRoot = join(root, 'workspaces')
+    await mkdir(join(workspaceRoot, FIRST), { recursive: true })
+    const merged: string[] = []
+    const store = {
+      mergeRetiredWorktreeNames: (_repoId: string, names: Iterable<string>) => {
+        merged.push(...names)
+        return true
+      }
+    }
+
+    try {
+      await ensureRetiredWorktreeNamesBackfilled(store, makeRepo('repo-local', '/repos/local'), {
+        workspaceDir: workspaceRoot,
+        nestWorkspaces: false
+      })
+
+      expect(merged).toEqual([FIRST])
+    } finally {
+      await rm(root, { force: true, recursive: true })
+    }
+  })
 })

src/main/worktree-name-retirement.ts

@@ -1,7 +1,7 @@
 import { readdir } from 'node:fs/promises'
 import { homedir } from 'node:os'
 import { join } from 'node:path'
-import { getRepoExecutionHostId } from '../shared/execution-host'
+import { getRepoExecutionHostId, LOCAL_EXECUTION_HOST_ID } from '../shared/execution-host'
 import {
   creatureNameTier,
   EMPTY_RETIRED_NAME_REGISTRY,
@@ -239,8 +239,13 @@ export async function ensureRetiredWorktreeNamesBackfilled(
   settings: RetirementPathSettings
 ): Promise<string | null> {
   // Remote workspaces keep their agent state on the execution host, which this scan cannot see, so
-  // a re-added SSH repo does not recover its retirements the way a local one does.
-  if (isFolderRepo(repo) || repo.connectionId) {
+  // a re-added remote repo does not recover its retirements the way a local one does.
+  //
+  // Why the host id and not `connectionId`: a runtime-owned repo carries `executionHostId` with no
+  // `connectionId`, so a connectionId check calls it local, scans THIS machine's directories, and
+  // files the result under the runtime's namespace — retiring names never used there while missing
+  // the ones that were.
+  if (isFolderRepo(repo) || getRepoExecutionHostId(repo) !== LOCAL_EXECUTION_HOST_ID) {
     return null
   }
   const probePath = await computeWorktreePathAsync(