Optimize bulk editor setup, deferred UI resources and Git plugin fixes

- Lazily compute document line hashes, avoid redundant multiline insertion
walks, and defer longest-line measurement for large or exceptionally long
text changes.

- Cache default code editor keybindings, reserve common command storage, and
create UIDiffView image viewers only when an image diff requires them.

- Keep cached screen positions coherent when descendants are queried before
dirty ancestors, and add regression coverage for ancestor movement.

- Relocate font-rendering golden images into the unit-test asset directory
and resolve image fixtures independently of the current working directory.

- Fix spurious status entries for files moved between directories. Preserve the suffix after Git's abbreviated brace notation when parsing renamed paths from numstat output. This prevents directory moves such as `bin/{ => unit_tests}/assets/...` from producing truncated synthetic untracked entries like `unit_tests`. Add regression coverage for staged files moved into a different directory.

- Git Plugin now remembers between sessions the uncommited commit message.

src/tools/ecode/plugins/git/gitplugin.cpp

@@ -8,6 +8,7 @@
 #include <eepp/graphics/image.hpp>
 #include <eepp/graphics/primitives.hpp>
 #include <eepp/scene/scenemanager.hpp>
+#include <eepp/system/base64.hpp>
 #include <eepp/system/filesystem.hpp>
 #include <eepp/system/luapattern.hpp>
 #include <eepp/system/scopedop.hpp>
@@ -255,6 +256,12 @@ GitPlugin::~GitPlugin() {
 		Sys::sleep( Milliseconds( 1.f ) );
 }
 
+void GitPlugin::onSaveState( IniFile* state ) {
+	std::string commitMessage;
+	Base64::encode( mLastCommitMsg.toUtf8(), commitMessage );
+	state->setValue( "git", "commit_message", commitMessage );
+}
+
 void GitPlugin::runAsyncTask( std::function<void()> task ) {
 	auto runningTasks = mRunningAsyncTasks;
 	++*runningTasks;
@@ -348,6 +355,12 @@ void GitPlugin::load( PluginManager* pluginManager ) {
 		}
 	}
 
+	std::string commitMessage;
+	Base64::decode(
+		getPluginContext()->getConfig().iniState.getValue( "git", "commit_message", "" ),
+		commitMessage );
+	mLastCommitMsg = String::fromUtf8( commitMessage );
+
 	if ( mKeyBindings.empty() ) {
 		mKeyBindings["git-blame"] = "alt+shift+b";
 	}