generalise manager
Add json in the base config manager name
Fix javascript iteration through array

for(var k in config) was assigning k to the properties of Array, not just the numeric indices

the second argument of add_buttons_group, k[1], should be config[k][1]
fix leading underscore

mering object with itself is stupid otherwise
JSON formatter expects JSONable dict/list

not already-serialized JSON string

pre-3.0 case of JSON string is handled with a warning.

msgspec5 made this change, but Python APIs that publish
JSON weren't updated to match.
put test in content manager
ensure warnings are raised in tests

avoids missed warnings if the warning was already shown
Make sure comm-dead is applied to the top widget view class
in all cases where the kernel disconnects.
Add a brief sleep after shutting down sessions in test teardown

This fixes a test failure for me on my Windows VM. See the comment for
details.
s/Json/JSON/g **/*.py
Bubble event and implement logic in CodeCell
invoke css
s/Notebooks/Files
Prevent the page from jumping on tree tab change
Merge pull request #7235 from jdfreder/jump-fix

Prevent the page from jumping on tree tab change
Merge pull request #7195 from Carreau/manager

generalise manager
Merge pull request #7226 from takluyver/win-sleep-session-tests

Add a brief sleep after shutting down sessions in test teardown
Merge pull request #7225 from Carreau/fix-actions

fix leading underscore
Merge pull request #7210 from minrk/json-display

JSON formatter expects JSONable dict/list
Merge pull request #7224 from jasongrout/fix-toolbarjs

Fix javascript iteration through array