portable storage, bug fixes, tooltips

all app data now lives next to the exe (presets, undo, settings,
window state, webview cache). dropped the directories crate.
auto-detects and fixes stale Explorer context menu entries when
the exe is moved. fixed regex case_insensitive field mismatch,
update check type mismatch, drive detection condition, rename
panic on root paths. added tooltips to zoom and browse buttons.
escape key now deselects files instead of wiping the pipeline

crates/nomina-core/src/bru.rs

@@ -24,7 +24,7 @@ pub fn parse_bru_file(path: &Path) -> crate::Result<NominaPreset> {
             rules.push(make_rule("regex", serde_json::json!({
                 "pattern": pattern,
                 "replacement": replace,
-                "case_sensitive": case,
+                "case_insensitive": !case,
                 "global": true,
                 "target": "Name",
             })));