Make Sage documentation functional

[kwankyu]

Sage documentation (website) is currently buggy in many ways.

I tried to fix various defects I noticed, including

• links in navigation bar
• index page, which is now in single column
• sage logo link always goes to the sagemath homepage
• class names now look ragged right
• long Bases for classes now horizontally scrolled
• updated sage theme based on the latest classic theme of Sphinx
• renamed sage theme to sage-classic theme (in anticipation of alternative themes)
• remove unnecessary sageref theme; only use sage theme
• remove obsolete python2.inv hyperlinks database
• added a new index.html which is installed right into the root directory SAGE_DOC.
• adjusted colors to increase contrast among elements
• documentation access from jupyter notebook (this undoes PDF documentation links in Documentation from Jupyter notebook are broken #33206)
• search box works (turned off Thebe)

As noted in the last item above, I turned off Thebe here. Work on reviving Thebe will continue in #33320 (perhaps very slowly).

To cleanly build the new documentation, try

$ make doc-uninstall && make doc-html && make doc-pdf

CC: @strogdon @haraldschilly @mkoeppe

Component: documentation

Author: Kwankyu Lee

Branch: acecf84

Reviewer: Tobias Diez, John Palmieri, François Bissey, Steven Trogdon

Issue created by migration from https://trac.sagemath.org/ticket/33309

[kwankyu]

Branch: u/klee/33309

[kwankyu]

Commit: 3b9e89f

[kwankyu]

New commits:

3b9e89f

Various fixes for sage documentation

[kwankyu]

Author: Kwankyu Lee

[kwankyu]

Description changed:

--- 
+++ 
@@ -1 +1,9 @@
+Sage documentation (website) is buggy in many ways.
 
+I tried to fix various defects I noticed, including
+
+- links in navigation bar, index, etc.
+
+- access from jupyter notebook
+
+- remove unnecessary `sageref` theme; only use `sage` theme

[kwankyu]

Description changed:

--- 
+++ 
@@ -2,7 +2,9 @@
 
 I tried to fix various defects I noticed, including
 
-- links in navigation bar, index, etc.
+- links in navigation bar
+
+- index page, which now in single column
 
 - access from jupyter notebook
 

[kwankyu]

Description changed:

--- 
+++ 
@@ -6,6 +6,6 @@
 
 - index page, which now in single column
 
-- access from jupyter notebook
+- documentation access from jupyter notebook (this undoes #33206)
 
 - remove unnecessary `sageref` theme; only use `sage` theme

[kwankyu]

Description changed:

--- 
+++ 
@@ -8,4 +8,6 @@
 
 - documentation access from jupyter notebook (this undoes #33206)
 
+Try `make doc-uninstall; make doc-html; make doc-pdf` to cleanly build the new documentation.
+
 - remove unnecessary `sageref` theme; only use `sage` theme

[kwankyu]

Description changed:

--- 
+++ 
@@ -8,6 +8,6 @@
 
 - documentation access from jupyter notebook (this undoes #33206)
 
+- remove unnecessary `sageref` theme; only use `sage` theme
+
 Try `make doc-uninstall; make doc-html; make doc-pdf` to cleanly build the new documentation.
-
-- remove unnecessary `sageref` theme; only use `sage` theme

[kwankyu]

Description changed:

--- 
+++ 
@@ -1,4 +1,4 @@
-Sage documentation (website) is buggy in many ways.
+Sage documentation (website) is currently buggy in many ways.
 
 I tried to fix various defects I noticed, including