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/e2e/test_chat_rag.py

@@ -98,16 +98,16 @@ def test_on_topic_question_streams_grounded_answer(
 
     # Grounded: a kubernetes.md source chip renders under the bubble
     # (top-N docs can add more chips; the question's doc must be among them).
-    # Phase 10: chips open the document viewer in a new tab (encoded URL);
-    # phase 13 appends back=/ so the viewer's back button returns to chat.
+    # Phase 26: the chip opens the document in the SAME-PAGE modal — no new
+    # tab; the encoded href stays as the no-JS / context-menu escape hatch
+    # (phase 13's back=/ lets the viewer's back button return to chat).
     chip = page.locator(".msg.brain .source-chip", has_text="kubernetes.md")
     expect(chip).to_have_count(1)
     expect(chip.first).to_contain_text("kubernetes.md")
     expect(chip.first).to_have_attribute(
         "href", "/document.html?source=docs&path=homelab%2Fkubernetes.md&back=%2F"
     )
-    expect(chip.first).to_have_attribute("target", "_blank")
-    expect(chip.first).to_have_attribute("rel", "noopener")
+    expect(chip.first).not_to_have_attribute("target")  # phase 26: modal, not a new tab
 
     # Button recovers: enabled + "Send" (never stale).
     expect(page.locator("#send-btn")).to_be_enabled()