feat(web): 2x reading column on wide desktops — 92rem at >=1500px (chat, shared, document view)

tests/unit/test_shared_page.py

@@ -19,7 +19,8 @@ silent regression is caught without a browser:
   chat page's interactive builders, and the rendered messages contain
   no button/form/link — the chips are plain spans, the source chips
   carry no ``href``;
-* the shared shell's 46rem column mapping + the static-chip and
+* the shared shell's reading-column mapping (--chat-column token,
+  phase 58) + the static-chip and
   invalid-state CSS (the ≤640px squeeze included).
 """
 from __future__ import annotations
@@ -378,15 +379,22 @@ def test_brand_note_resolves_at_call_time() -> None:
 # ---------- styles.css: the shared page ----------
 
 
-def test_shared_shell_maps_to_the_46rem_column() -> None:
-    """The PLAN §7 column contract: .shared-shell is the centered
-    46rem chat column (the conversation reads exactly like the chat
-    page's, so the existing .msg/.bubble CSS applies unchanged)."""
+def test_shared_shell_maps_to_the_reading_column() -> None:
+    """The PLAN §7 column contract (phase 58): .shared-shell is the
+    centered chat column riding the --chat-column token (46rem base,
+    92rem at >=1500px wide desktops — owner instruction 2026-08-31,
+    TODO L5 / D2). The conversation reads exactly like the chat
+    page's, so the existing .msg/.bubble CSS applies unchanged."""
     css = _css()
     block = re.search(r"\.shared-shell \{([\s\S]*?)\n\}", css)
     assert block, "styles.css must style .shared-shell"
     body = block.group(1)
-    assert "max-width: 46rem" in body, "the PLAN §7 centered chat column"
+    assert "max-width: var(--chat-column)" in body, (
+        "the PLAN §7 centered chat column (phase 58 token)"
+    )
+    assert "46rem" not in body.split("/*")[0], (
+        "no hard-coded cap — the width rides the token"
+    )
     assert "margin-inline: auto" in body, "centered"
     assert "display: flex" in body and "flex-direction: column" in body