Add external agent memory migration (#33444)

## What changed

- Add a feature-gated `MEMORY` migration item to the app-server protocol and TUI.
- Discover project memory Markdown files, preserve their project scope, and copy selected projects into the Codex memory extension workspace.
- Detect changed, renamed, and removed source projects, report per-project import failures, and enqueue memory consolidation after workspace changes.

## Testing

- Cover memory discovery, selection, synchronization, scope validation, feature gating, protocol results, and TUI rendering.

GitOrigin-RevId: 9b17b2e9a639a064dba8aaffbec6345ae419018e

codex-rs/external-agent-migration/src/memory_tests.rs

@@ -0,0 +1,118 @@
+use super::*;
+use pretty_assertions::assert_eq;
+use tempfile::TempDir;
+
+#[test]
+fn discovers_arbitrary_project_markdown() {
+    let root = TempDir::new().expect("create tempdir");
+    let external_agent_home = root.path().join(".external-agent");
+    let project_root = external_agent_home.join("projects/opaque-project-key");
+    let project_memory = project_root.join("memory");
+    let project_cwd = root.path().join("project");
+    fs::create_dir_all(project_memory.join("topics")).expect("create memory directories");
+    fs::create_dir_all(&project_cwd).expect("create project cwd");
+    fs::write(
+        project_root.join("session.jsonl"),
+        serde_json::json!({
+            "type": "user",
+            "cwd": &project_cwd,
+            "timestamp": "2026-07-13T00:00:00Z",
+            "message": { "content": "remember this" },
+        })
+        .to_string(),
+    )
+    .expect("write session");
+    fs::write(project_memory.join("MEMORY.md"), "index").expect("write index");
+    fs::write(project_memory.join("release-process.md"), "release notes")
+        .expect("write arbitrary topic");
+    fs::write(project_memory.join("topics/database.md"), "database notes")
+        .expect("write nested topic");
+    fs::write(project_memory.join("ignored.txt"), "not markdown").expect("write ignored file");
+    let discovered =
+        discover_external_memory_files(&external_agent_home).expect("discover memories");
+    let project_cwd = fs::canonicalize(project_cwd).expect("canonicalize project cwd");
+
+    assert_eq!(
+        discovered
+            .iter()
+            .map(|memory| {
+                (
+                    memory.project_key.as_str(),
+                    memory.project_cwd.as_deref(),
+                    memory.relative_path.as_path(),
+                )
+            })
+            .collect::<Vec<_>>(),
+        vec![
+            (
+                "opaque-project-key",
+                Some(project_cwd.as_path()),
+                Path::new("MEMORY.md")
+            ),
+            (
+                "opaque-project-key",
+                Some(project_cwd.as_path()),
+                Path::new("release-process.md")
+            ),
+            (
+                "opaque-project-key",
+                Some(project_cwd.as_path()),
+                Path::new("topics/database.md")
+            ),
+        ]
+    );
+}
+
+#[test]
+fn leaves_project_unscoped_without_an_existing_absolute_cwd() {
+    let root = TempDir::new().expect("create tempdir");
+    let external_agent_home = root.path().join(".external-agent");
+    let project_root = external_agent_home.join("projects/opaque-project-key");
+    let project_memory = project_root.join("memory");
+    fs::create_dir_all(&project_memory).expect("create memory directory");
+    fs::write(
+        project_root.join("session.jsonl"),
+        serde_json::json!({
+            "type": "user",
+            "cwd": root.path().join("missing-project"),
+            "timestamp": "2026-07-13T00:00:00Z",
+            "message": { "content": "remember this" },
+        })
+        .to_string(),
+    )
+    .expect("write session");
+    fs::write(project_memory.join("MEMORY.md"), "index").expect("write index");
+
+    let discovered =
+        discover_external_memory_files(&external_agent_home).expect("discover memories");
+
+    assert_eq!(
+        discovered,
+        vec![ExternalMemoryFile {
+            project_key: "opaque-project-key".to_string(),
+            project_cwd: None,
+            source_path: project_memory.join("MEMORY.md"),
+            relative_path: PathBuf::from("MEMORY.md"),
+        }]
+    );
+}
+
+#[cfg(unix)]
+#[test]
+fn skips_symlinked_memory_directory() {
+    use std::os::unix::fs::symlink;
+
+    let root = TempDir::new().expect("create tempdir");
+    let external_agent_home = root.path().join(".external-agent");
+    let project_root = external_agent_home.join("projects/project");
+    let outside_memory = root.path().join("outside-memory");
+    fs::create_dir_all(&project_root).expect("create project");
+    fs::create_dir_all(&outside_memory).expect("create outside memory");
+    fs::write(outside_memory.join("secret.md"), "secret").expect("write outside memory");
+    symlink(&outside_memory, project_root.join("memory")).expect("symlink memory directory");
+
+    assert_eq!(
+        discover_external_memory_files(&external_agent_home).expect("discover memories"),
+        Vec::new()
+    );
+}