fix(github): align PR source and review head origin (#10677)

* fix(github): align PR source and review head origin

* fix(github): pin number-based work item open to the repo source preference

Open-by-number and details still ran the upstream-first multi-candidate PR
probe, so a fork and its upstream sharing a PR number opened different PRs
than the list and start-point paths did once #10677 pinned those to origin.

Thread repo.issueSourcePreference through dispatchWorkItem, getWorkItemDetails,
getRepoWorkItem, and getRepoWorkItemDetails. getWorkItemByOwnerRepo is left
alone: explicit owner/repo already pins identity. auto/upstream/undefined keep
the multi-candidate probe.

Co-authored-by: Orca <help@stably.ai>

* test(github): enforce origin preference in review head origin resolution

The explicit origin preference must short-circuit before any identity probe, so no remote queries should occur. Add validation to reject unexpected remotes and tighten the test assertion to verify no remote get-url calls happen at all.

* fix(github): enforce origin preference in issue open-by-number lookup

listWorkItems and getWorkItem must share preference so origin/upstream
toggles cannot disagree. Explicit origin preference now fail-closes when
origin identity is unresolved (no bare-lookup fallback), matching the
PR candidate resolution rule.

---------

Co-authored-by: Orca <help@stably.ai>

src/main/github/client-issue-source.test.ts

@@ -513,6 +513,54 @@ describe('GitHub issue source split', () => {
     expect(item?.prRepo).toEqual(upstream)
   })
 
+  it('pins typed PR metadata to explicit origin when upstream has the same number', async () => {
+    const upstream = { owner: 'stablyai', repo: 'orca', host: 'github.com' }
+    const origin = { owner: 'fork', repo: 'orca', host: 'github.com' }
+    getOwnerRepoMock.mockResolvedValue(origin)
+    mockUpstreamCandidate(upstream)
+    resolvePRRepositoryCandidatesMock.mockResolvedValue({
+      candidates: [upstream, origin],
+      headRepo: origin
+    })
+    ghExecFileAsyncMock.mockResolvedValueOnce({
+      stdout: JSON.stringify({
+        number: 42,
+        title: 'Origin PR',
+        state: 'open',
+        url: 'https://github.com/fork/orca/pull/42',
+        labels: [],
+        updatedAt: '2026-04-02T00:00:00Z',
+        author: { login: 'octocat' },
+        isDraft: false,
+        headRefName: 'origin/fix',
+        baseRefName: 'main'
+      })
+    })
+
+    const item = await getWorkItem('/repo-root', 42, 'pr', null, {}, 'origin')
+
+    expect(resolvePRRepositoryCandidatesMock).not.toHaveBeenCalled()
+    expect(ghExecFileAsyncMock.mock.calls[0]?.[0]).toEqual(
+      expect.arrayContaining(['pr', 'view', '--repo', 'fork/orca'])
+    )
+    expect(
+      ghExecFileAsyncMock.mock.calls.some((call) =>
+        (call[0] as string[]).some((arg) => arg.includes('upstream/orca'))
+      )
+    ).toBe(false)
+    expect(item?.prRepo).toEqual(origin)
+  })
+
+  it('does not run a bare PR lookup when explicit origin identity is unresolved', async () => {
+    getOwnerRepoMock.mockResolvedValue(null)
+    mockUpstreamCandidate({ owner: 'stablyai', repo: 'orca' })
+
+    await expect(getWorkItem('/repo-root', 42, 'pr', null, {}, 'origin')).resolves.toBeNull()
+
+    expect(resolvePRRepositoryCandidatesMock).not.toHaveBeenCalled()
+    expect(ghExecFileAsyncMock).not.toHaveBeenCalled()
+  })
+
   it('does not run a bare gh lookup for an SSH repo without candidates', async () => {
     resolvePRRepositoryCandidatesMock.mockResolvedValueOnce({ candidates: [], headRepo: null })