Align build environment with the English source (#165)

environment.yml copied from lecture-python.myst (anaconda 2026.06,
jupyter-book <2.0, quantecon-book-theme 0.21.0, sphinx-tojupyter 0.6.0
and current sphinx-* pins) so the resynced 2026-era lecture code builds
against the same stack the source executes under. Adds the source's
nb_merge_streams setting to _config.yml.

Supersedes the environment half of #97 (which pinned anaconda 2025.12 /
theme 0.15.1 — current in December, seven months behind now).

Part of Phase 0 Track B, QuantEcon/lecture-python.myst#947.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: mmcky

environment.yml

@@ -3,15 +3,17 @@ channels:
   - default
 dependencies:
   - python=3.13
-  - anaconda=2025.06
+  - anaconda=2026.06
   - pip
   - pip:
-    - jupyter-book==1.0.4post1
-    - quantecon-book-theme==0.10.1
-    - sphinx-tojupyter==0.3.1
-    - sphinxext-rediraffe==0.2.7
-    - sphinx-exercise==1.2.0
-    - sphinx-proof==0.3.0
-    - sphinxcontrib-youtube==1.4.1
-    - sphinx-togglebutton==0.3.2
-    - sphinx-reredirects==0.1.4
+    - jupyter-book>=1.0.4post1,<2.0
+    - quantecon-book-theme==0.21.0
+    - sphinx-tojupyter==0.6.0
+    - sphinxext-rediraffe==0.3.0
+    - sphinx-exercise==1.2.1
+    - sphinx-proof==0.4.0
+    - sphinxcontrib-youtube==1.5.0
+    - sphinx-togglebutton==0.4.5
+    - sphinx-reredirects==1.1.0
+
+

lectures/_config.yml

@@ -38,6 +38,7 @@ sphinx:
     # false-positive links
     linkcheck_ignore: ['https://online.stat.psu.edu/stat415/book/export/html/834']
     bibtex_reference_style: author_year
+    nb_merge_streams: true
     nb_mime_priority_overrides: [
        # HTML
        ['html', 'application/vnd.jupyter.widget-view+json', 10],