fix: partage dirigé — dossier Partage virtuel + ouverture en onglet #196

- _resolve_shared_file: home-<user>/Partage/<f> -> fichier source (/api/file, raw, download)
- clic dossier Partage: dépliage sans navigation (fix Directory not found)
- fichiers reçus ouverts en onglet applicatif (arbre, recherche, dashboard)
- POST /api/share: path vide/null rejeté (400) — un share path:null cassait /api/shares
- +2 tests (13 total)

tests/test_directed_shares.py

@@ -167,3 +167,33 @@ class TestDirectedShareGate:
         resp = user_client.get("/api/search", params={"q": "dirigé", "vault": "all"})
         assert resp.status_code == 200
         assert not [r for r in resp.json()["results"] if r.get("share_token")]
+
+    def test_recipient_opens_shared_file_in_app(self, sessions):
+        # #196 : /api/file résout home-<user>/Partage/<fichier> vers la source.
+        admin_client, user_client = sessions
+        path = _ensure_shared_file()
+        resp = admin_client.post("/api/share/TestVault", json={
+            "path": path, "shared_with": ["normaluser"],
+        })
+        assert resp.status_code == 200
+        r = user_client.get("/api/file/home-normaluser", params={"path": "Partage/share_directed.md"})
+        assert r.status_code == 200, r.text
+        body = r.json()
+        assert body["is_markdown"] is True
+        assert "dirigé" in body["html"]
+
+        # raw endpoint too
+        r = user_client.get("/api/file/home-normaluser/raw", params={"path": "Partage/share_directed.md"})
+        assert r.status_code == 200
+        assert "dirigé" in r.json()["raw"]
+
+    def test_shared_file_resolution_is_user_scoped(self, sessions):
+        # home-admin/Partage/x.md demandé par normaluser → pas de mapping
+        # (le home d'un autre user lui est interdit, 403 avant tout).
+        admin_client, user_client = sessions
+        path = _ensure_shared_file()
+        admin_client.post("/api/share/TestVault", json={
+            "path": path, "shared_with": ["normaluser"],
+        })
+        r = user_client.get("/api/file/home-admin", params={"path": "Partage/share_directed.md"})
+        assert r.status_code == 403