Keep opened issue details and edits in the selected repository (#24729)

Keeps a fork issue’s details, metadata and edits bound to the repository the user opened, including same-number issues in fork and upstream. Repairs selected-assignee leakage and delayed failed edits repainting another issue.

Fixes #24378

Incorporates and cross-reviews contributor PR #24379, including its source-resolver correction and regression material. Covers the contributor PR’s Project-row identity and retained-dialog mutation findings. The final published head passes focused tests, hidden macOS rendering and current CI; the callback-timing bot thread has an evidence-based response.

Co-authored-by: Katsuma Takehisa <k.takehisa@nissogr.com>

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

@@ -22,4 +22,25 @@ describe('isValidGitHubApiRepository', () => {
     expect(isValidGitHubApiRepository({ owner: 'acme', repo: '..' })).toBe(false)
     expect(isValidGitHubApiRepository({ owner: 'acme', repo: 'a/b' })).toBe(false)
   })
+
+  it.each([42, false, null, {}])('rejects a non-string repository host: %j', (host) => {
+    expect(isValidGitHubApiRepository({ owner: 'acme', repo: 'orca', host })).toBe(false)
+  })
+
+  it.each([undefined, 'github.com', 'github.enterprise.test:8443'])(
+    'accepts supported legacy or explicit repository host types: %j',
+    (host) => {
+      expect(isValidGitHubApiRepository({ owner: 'acme', repo: 'orca', host })).toBe(true)
+    }
+  )
+
+  it.each([
+    null,
+    'acme/orca',
+    { owner: 42, repo: 'orca' },
+    { owner: 'acme', repo: 42 },
+    { owner: 'acme' }
+  ])('rejects malformed runtime repository identities: %j', (repository) => {
+    expect(isValidGitHubApiRepository(repository)).toBe(false)
+  })
 })