refactor(workspaces): unify display-name pin derivation

Three call sites (renderer optimistic update, local IPC updateMeta
handler, remote worktree.set handler) each restated the same formula;
a future edit to one would silently skew provenance between paths.

src/main/ipc/worktrees/metadata/register-worktree-metadata-handlers.ts

@@ -1,5 +1,6 @@
 import { ipcMain } from 'electron'
 import type { WorktreeMeta } from '../../../../shared/worktree/meta-types'
+import { displayNameUpdatePinsLabel } from '../../../../shared/worktree/display-name-provenance'
 import { parseExecutionHostId } from '../../../../shared/execution-host'
 import { stripOrcaProvenanceMetaUpdates } from '../../../worktree-removal-safety'
 import { getRepoIdFromWorktreeId } from '../../../../shared/worktree/id'
@@ -40,7 +41,7 @@ export function registerWorktreeMetadataHandlers(context: WorktreeIpcContext): v
           ? {
               ...validatedUpdates,
               // The host persists provenance; do not rely on renderer-authored metadata.
-              displayNameIsPinned: Boolean(validatedUpdates.displayName.trim()),
+              displayNameIsPinned: displayNameUpdatePinsLabel(validatedUpdates.displayName),
               pendingFirstAgentMessageRename: false,
               firstAgentMessageRenameError: null
             }

src/main/runtime/rpc/methods/worktree.ts

@@ -4,6 +4,7 @@ import {
   resolveAutomationWorkspaceProvenance
 } from '../../../automations/workspace-provenance'
 import { buildCliWorkspaceProvenance } from '../../../../shared/cli-workspace-provenance'
+import { displayNameUpdatePinsLabel } from '../../../../shared/worktree/display-name-provenance'
 import { defineMethod, type RpcMethod } from '../core'
 import { buildManagedWorktreeCreateArgs } from './worktree-create-args'
 import { resolvePairedCallerHostId } from './paired-caller-host-id'
@@ -134,7 +135,7 @@ export const WORKTREE_METHODS: RpcMethod[] = [
       worktree: await runtime.updateManagedWorktreeMeta(params.worktree, {
         displayName: params.displayName,
         ...(params.displayName !== undefined
-          ? { displayNameIsPinned: Boolean(params.displayName.trim()) }
+          ? { displayNameIsPinned: displayNameUpdatePinsLabel(params.displayName) }
           : {}),
         linkedIssue: params.linkedIssue,
         linkedPR: params.linkedPR,

src/renderer/src/store/slices/worktrees/metadata/update-worktree-meta.ts

@@ -2,6 +2,7 @@ import type { WorktreeSlice } from '../../worktree-helpers'
 import type { WorktreeSliceGet, WorktreeSliceSet } from '../listing/worktree-slice-types'
 import { translate } from '@/i18n/i18n'
 import { isPositiveHostedReviewNumber } from '../../../../../../shared/hosted-review'
+import { displayNameUpdatePinsLabel } from '../../../../../../shared/worktree/display-name-provenance'
 import { parseWorkspaceKey } from '../../../../../../shared/workspace-scope'
 import { applyWorktreeUpdates, getRepoIdFromWorktreeId } from '../../worktree-helpers'
 import { getHostedReviewCacheKey } from '../../hosted-review-cache-identity'
@@ -124,7 +125,7 @@ export function createUpdateWorktreeMeta(
     // Why: bump lastActivityAt on comment edits so the time-decay sort doesn't drop a just-touched worktree.
     const displayNameProvenance =
       'displayName' in normalizedUpdates
-        ? { displayNameIsPinned: Boolean(normalizedUpdates.displayName?.trim()) }
+        ? { displayNameIsPinned: displayNameUpdatePinsLabel(normalizedUpdates.displayName) }
         : {}
     const targetEnriched = resolvedPushTarget
       ? { ...normalizedUpdates, ...displayNameProvenance, pushTarget: resolvedPushTarget }

src/shared/worktree/display-name-provenance.ts

@@ -0,0 +1,4 @@
+/** A rename with text pins the label; empty text returns it to automatic (branch-derived). */
+export function displayNameUpdatePinsLabel(displayName: string | undefined): boolean {
+  return Boolean(displayName?.trim())
+}