Rename framework/ to diachron/ and update all references

Update paths in .gitignore, cmd, develop, mgmt, sync.sh, check.sh,
fixup.sh, CLAUDE.md, docs/new-project.md, and backend/*.sh scripts.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

fixup.sh

@@ -11,7 +11,7 @@ cd "$DIR"
 # uv run ruff format .
 
 shell_scripts="$(fd '.sh$' | xargs)"
-shfmt -i 4 -w "$DIR/cmd" "$DIR"/framework/cmd.d/* "$DIR"/framework/shims/* "$DIR"/master/master "$DIR"/logger/logger
+shfmt -i 4 -w "$DIR/cmd" "$DIR"/diachron/cmd.d/* "$DIR"/diachron/shims/* "$DIR"/master/master "$DIR"/logger/logger
 # "$shell_scripts"
 for ss in $shell_scripts; do
     shfmt -i 4 -w $ss
@@ -21,6 +21,6 @@ pushd "$DIR/master"
 go fmt
 popd
 
-pushd "$DIR/express"
+pushd "$DIR/backend"
 ../cmd pnpm biome check --write
 popd