Keep PR refreshes anchored to cached review numbers (#2541)

- Use fallback PR numbers after branch lookup misses, including detached HEAD
- Preserve review cards for forked or deleted-head PRs across manual refreshes
- Clear stale GitHub PR cache entries when unlinking worktree review metadata

src/shared/hosted-review.ts

@@ -28,6 +28,7 @@ export type HostedReviewForBranchArgs = {
   repoId?: string
   branch: string
   linkedGitHubPR?: number | null
+  fallbackGitHubPR?: number | null
   linkedGitLabMR?: number | null
   linkedBitbucketPR?: number | null
   linkedAzureDevOpsPR?: number | null
@@ -118,6 +119,7 @@ export type HostedReviewCreationEligibilityArgs = {
   ahead?: number
   behind?: number
   linkedGitHubPR?: number | null
+  fallbackGitHubPR?: number | null
   linkedGitLabMR?: number | null
   linkedBitbucketPR?: number | null
   linkedAzureDevOpsPR?: number | null

src/shared/types.ts

@@ -646,6 +646,7 @@ export type GitHubPRRefreshAlias = {
 
 export type GitHubPRRefreshCandidate = GitHubPRRefreshAlias & {
   linkedPRNumber?: number | null
+  fallbackPRNumber?: number | null
   repoKind: RepoKind
   repoId: string
   isBare?: boolean