Fix GitHub Enterprise host identity loss across PR/work-item paths

- Thread `host` through mobile PR RPC params, IPC work-item lookups, and
  RPC schemas so GHES identity survives the renderer/mobile/main boundary
  instead of silently falling back to a same-named github.com repo.
- Qualify `--repo`/`-R` args for github.com too (not just GHES), since
  gh resolves bare shorthand against a process-level GH_HOST that can
  redirect pinned github.com commands.
- Cache `getOriginGitHubApiRepository` to avoid a per-call uncached
  `git remote get-url` round trip on connection-backed repos.
- Add a local-fork fallback in `getWorkItemDetails` so PRs living on a
  base repo (not visible via the origin slug) still resolve via cwd.
- Centralize the github.com-vs-GHES host predicate in
  `isDefaultGitHubHost` so cache keys, quota scoping, and identity
  checks can't drift out of sync.

src/main/github/github-api-repository.ts

@@ -1,9 +1,31 @@
 import type { GitHubOwnerRepo } from '../../shared/types'
+import { isDefaultGitHubHost } from '../../shared/github-repository-identity-key'
 import { getOwnerRepo, type LocalGitExecOptions } from './gh-utils'
 import { getEnterpriseGitHubRepoSlug } from './github-enterprise-repository'
 
 export type GitHubApiRepository = GitHubOwnerRepo
 
+// Why: the enterprise branch spawns an uncached `git remote get-url` (an SSH
+// round trip on connection-backed repos) — hot paths like per-file contents
+// and viewed-state toggles resolve per call, so cache like ownerRepoCache does.
+const ORIGIN_REPO_CACHE_TTL_MS = 30_000
+const originRepoCache = new Map<string, { value: GitHubApiRepository | null; expiresAt: number }>()
+const originRepoInFlight = new Map<string, Promise<GitHubApiRepository | null>>()
+
+function originRepoCacheKey(
+  repoPath: string,
+  connectionId?: string | null,
+  localGitOptions: LocalGitExecOptions = {}
+): string {
+  return `${connectionId ?? 'local'}\0${localGitOptions.wslDistro ?? ''}\0${repoPath}`
+}
+
+/** @internal - exposed for tests only */
+export function _resetOriginGitHubApiRepositoryCache(): void {
+  originRepoCache.clear()
+  originRepoInFlight.clear()
+}
+
 export async function getOriginGitHubApiRepository(
   repoPath: string,
   connectionId?: string | null,
@@ -13,9 +35,30 @@ export async function getOriginGitHubApiRepository(
   if (ownerRepo) {
     return { ...ownerRepo, host: 'github.com' }
   }
-  const enterpriseOptions =
-    Object.keys(localGitOptions).length > 0 ? { localGitExecOptions: localGitOptions } : {}
-  return getEnterpriseGitHubRepoSlug(repoPath, connectionId, enterpriseOptions)
+  const cacheKey = originRepoCacheKey(repoPath, connectionId, localGitOptions)
+  const cached = originRepoCache.get(cacheKey)
+  if (cached && cached.expiresAt > Date.now()) {
+    return cached.value
+  }
+  const inFlight = originRepoInFlight.get(cacheKey)
+  if (inFlight) {
+    return inFlight
+  }
+  const probe = (async () => {
+    const enterpriseOptions =
+      Object.keys(localGitOptions).length > 0 ? { localGitExecOptions: localGitOptions } : {}
+    const slug = await getEnterpriseGitHubRepoSlug(repoPath, connectionId, enterpriseOptions)
+    originRepoCache.set(cacheKey, { value: slug, expiresAt: Date.now() + ORIGIN_REPO_CACHE_TTL_MS })
+    return slug
+  })()
+  originRepoInFlight.set(cacheKey, probe)
+  try {
+    return await probe
+  } finally {
+    if (originRepoInFlight.get(cacheKey) === probe) {
+      originRepoInFlight.delete(cacheKey)
+    }
+  }
 }
 
 export async function resolveGitHubApiRepository(
@@ -46,7 +89,7 @@ export async function resolveGitHubApiRepository(
 }
 
 export function isGitHubDotComRepository(repository: GitHubApiRepository): boolean {
-  return !repository.host || repository.host.toLowerCase() === 'github.com'
+  return isDefaultGitHubHost(repository.host)
 }
 
 // Why: the gh runner host-qualifies argv from `options.host`, so every known