feat(ui): one consistent navbar on every page (TODO.md L3)

tests/e2e/test_header_consistency.py

@@ -18,6 +18,14 @@ Phase 16 adaptation: the auth control (Sign in / Sign out) joins the chat
 header's ``.header-inner`` — the desktop test verifies its presence in
 both auth states without the bar's height moving (height assertions
 unchanged).
+
+Phase 34 adaptation (two-row viewer header, owner confirmation
+2026-08-26): the viewer's ``<header>`` is now TWO rows — row 1 is the
+standard shared bar (``.doc-header .app-header``, the phase-12/19
+``--header-h`` contract) and row 2 is the ``.doc-titlebar`` (back +
+title + meta, content-sized). The height assertions are pointed at ROW
+1 — the standard bar — which must equal the chat/sources bars exactly;
+the titlebar row is asserted present (height > 0), not height-pinned.
 """
 from __future__ import annotations
 
@@ -95,7 +103,9 @@ def _header_heights(page: Page, app_url: str) -> dict[str, float]:
 
     page.goto(app_url + VIEWER_URL)
     expect(page.locator("#doc-title")).to_have_text("Kubernetes Homelab Cluster", timeout=15_000)
-    heights["document"] = _box_height(page, ".doc-header")
+    # Phase 34: the viewer header is two rows — measure ROW 1 (the
+    # standard bar), which must equal the other pages' bars exactly.
+    heights["document"] = _box_height(page, ".doc-header .app-header")
     return heights
 
 
@@ -158,6 +168,9 @@ def test_header_height_identical_across_pages_mobile(
 def test_viewer_header_content_still_fits(
     page: Page, app_url: str, mock_llm: int, db_ready: None
 ) -> None:
+    """Phase 34: the phase-10 viewer content (title, badges, back link)
+    survives in the titlebar ROW, and row 1 stays the pinned standard
+    bar — single-line on both desktop and mobile."""
     _seed_db(mock_llm)
 
     for width, expected_h in ((1280, DESKTOP_HEADER_H), (375, MOBILE_HEADER_H)):
@@ -176,10 +189,14 @@ def test_viewer_header_content_still_fits(
         expect(page.locator(".format-badge", has_text="md")).to_be_visible()
         expect(page.locator(".doc-path", has_text="homelab/kubernetes.md")).to_be_visible()
 
-        # Back link still there, ≥44px touch target, in the shared bar.
+        # Back link still there, ≥44px touch target, in the titlebar row.
         back = page.locator("#doc-back")
         expect(back).to_be_visible()
         assert _box_height(page, "#doc-back") >= 44
-        expect(page.locator(".doc-header")).to_have_css(
+
+        # Phase 34 two-row contract: ROW 1 is the standard bar (the
+        # pinned --header-h), and the titlebar row is present below it.
+        expect(page.locator(".doc-header .app-header")).to_have_css(
             "height", f"{expected_h}px"
         )
+        assert _box_height(page, ".doc-titlebar") > 0, ("the titlebar row must render")