fix(github): verify cached integration PRs after tracking is removed

Use the existing REST PR mapping to read the head repository's default
branch when no tracked remote or origin can identify it. Require matching
repository and head metadata, and preserve the PR if the lookup fails.

This clears both closed and merged integration PRs cached by a fork
checkout after its upstream tracking is removed.

Co-authored-by: petersindex <287557875+petersindex@users.noreply.github.com>

src/main/github/client/lookup/branch-lookup-resolution.ts

@@ -87,7 +87,8 @@ export async function resolvePRForBranchOutcome(input: {
     linkedPRNumber,
     repoPath,
     connectionId,
-    localGitOptions
+    localGitOptions,
+    ghOptions
   }
   const implicitPRPolicy = createImplicitDefaultBranchPRPolicy(defaultBranchPRContext)
 

src/main/github/client/lookup/implicit-default-branch-pr.ts

@@ -4,13 +4,14 @@ import {
   getRemoteHeadBranchName,
   getRepoDefaultBranchName
 } from '../../../source-control/repo-default-branch'
-import type { HostedReviewLocalGitOptions } from './../github-exec-scope'
+import type { GhExecOptions, HostedReviewLocalGitOptions } from './../github-exec-scope'
 import type { TrackedUpstreamBranch } from './tracked-upstream-cache'
 import {
   pullRequestHeadRepository,
   type PullRequestLookupData,
   type PullRequestLookupPolicy
 } from './pull-request-lookup-data'
+import { getRestPRByNumber } from './pr-number-lookup'
 
 export type ImplicitDefaultBranchPRContext = {
   originHeadRepo: OwnerRepo | null
@@ -20,6 +21,7 @@ export type ImplicitDefaultBranchPRContext = {
   repoPath: string
   connectionId?: string | null
   localGitOptions: HostedReviewLocalGitOptions
+  ghOptions: GhExecOptions
 }
 
 export function createImplicitDefaultBranchPRPolicy(
@@ -73,7 +75,19 @@ async function shouldHideImplicitDefaultBranchPR(
         ? 'origin'
         : null
   if (!remoteName) {
-    return false
+    try {
+      // Removed tracking can leave a cached integration PR without a matching remote.
+      const metadata = await getRestPRByNumber(prRepo, data.number, input.ghOptions)
+      const metadataHeadRepo = pullRequestHeadRepository(metadata, prRepo)
+      return (
+        metadataHeadRepo !== null &&
+        githubRepoIdentityKey(metadataHeadRepo) === headRepoKey &&
+        metadata.headRefName === data.headRefName &&
+        metadata.headDefaultBranchName === data.headRefName
+      )
+    } catch {
+      return false
+    }
   }
   // An unknown upstream HEAD cannot borrow a different repository's origin default.
   const defaultBranchName =