jmsfx-editor: design and build a YAML <-> model persistence bridge

[ctgnz]

The gap

jmsfx-editor's stated purpose (CLAUDE.md) is editing the model file itself (`model-standard.yml`). Investigated the module end to end: there is no YAML read or write path anywhere in it - no SnakeYAML/Jackson-YAML imports, no file I/O at all.

What exists is `DynamicIconLibrary` + ~20 `*Impl` classes: a mutable, `ObservableList`/JavaFX-property-backed implementation of jmsfx-core's `IconLibrary`/`SymbolSet`/etc. interfaces. But `DynamicIconLibrary`'s only constructor (`DynamicIconLibrary(IconLibrary staticLibrary)`) builds a live mutable copy of an already-generated `IconLibrary` (i.e. `StandardIconLibrary.instance()`, jmsfx-standard's generated singleton) - it never reads YAML. So even "loading" today really means "clone the generated output," not "load the source of truth."

The actual YAML read/write logic that exists - `JmsfxParser.readLibraryModel`/`writeLibraryModel` in `jmsfx-generator` - operates on a completely different type hierarchy: `jmsfx-generator`'s own `LibraryModel`/`SymbolSetModel` generation-time DTOs, not jmsfx-core's `IconLibrary`/`SymbolSet` interfaces that `DynamicIconLibrary` implements. `jmsfx-editor`'s `pom.xml` doesn't even depend on `jmsfx-generator`. These two type systems were never connected.

Scope

This is real design work, not wiring:

• Design the `LibraryModel` (jmsfx-generator DTOs) <-> `DynamicIconLibrary`/`*Impl` (jmsfx-editor's live model) conversion in both directions
• Load path: YAML -> `JmsfxParser.readLibraryModel` -> `LibraryModel` -> populate a `DynamicIconLibrary` tree
• Save path: `DynamicIconLibrary` tree -> `LibraryModel` -> `JmsfxParser.writeLibraryModel` -> YAML
• Add the `jmsfx-generator` dependency to `jmsfx-editor`'s `pom.xml`
• Fix `DynamicIconLibrary.getCountryCodes()` (`DynamicIconLibrary.java:102`), currently a hardcoded placeholder (`// TODO: add full list`) returning only `CountryCode.UNDEFINED` - the real country list needs to come from somewhere (likely this same load path, once it exists)

Depends on / blocks

This is a prerequisite for #8 (the actual editor GUI) having anything real to load and save.