feat(ui): documents open in an almost-fullscreen modal instead of a new page — same-page overlay on chat + Sources, /document.html kept as the no-JS/direct-link fallback

tests/integration/test_api.py

@@ -77,6 +77,7 @@ def test_styles_and_js_served(client) -> None:
     assert client.get("/assets/markdown.js").status_code == 200  # phase 10: shared renderer
     assert client.get("/assets/document.js").status_code == 200  # phase 10: viewer page
     assert client.get("/assets/login.js").status_code == 200  # phase 16: login page
+    assert client.get("/assets/document-modal.js").status_code == 200  # phase 26: modal module
 
 
 # Emoji code points banned from UI chrome (phase 08): the pictograph
@@ -112,6 +113,7 @@ def _find_emoji(text: str) -> list[str]:
         "/assets/markdown.js",
         "/assets/document.js",
         "/assets/login.js",  # phase 16
+        "/assets/document-modal.js",  # phase 26: the document modal module
         "/assets/styles.css",
     ],
 )