refactor: unify component type dispatch + decompose RfSimulatorApp (#51)

[striderZA]

Summary

Fixes the RfSimulatorApp god-object + six parallel hardcoded type-dispatch tables: adding a component used to touch ~10 files. All dispatch now flows through one extended ComponentTypeRegistry, and the app is decomposed by extracting PFBViewManager and ProjectSerializer.

Related issue

Closes #51

Type of change

• Bug fix
• New feature
• Refactor
• Documentation

What changed

Phase 1 — unified registry + type_name()

• IComponentEngine::type_name() pure virtual (canonical lowercase key) on all 11 engines + 2 test engines
• ComponentTypeRegistry extended to 11 descriptors: project_type, display_name, menu_label, label_prefix, kind, authorable, fields, create() factory, draw_inspector callback; new findByProjectType() (accepts legacy + canonical names)
• saveProject/loadProject/duplicateComponent dispatch through the registry (.rfsim type strings byte-identical, legacy files still load)
• ComponentLibrary::instantiate switched to create() + deserialize() — library JSON behavior preserved with 5 key-parity fixes (ADC fs_Hz, mixer conversion_gain_dB, attenuator attenuation_dB, filter string-enum, amplifier enable_nonlinear derivation)
• Canvas menu data-driven via NodeGraphWidget::setAddableComponents + unified RfSimulatorApp::addComponent with unconditional markDirty() — fixes the Equalizer not-marking-dirty bug
• Inspector dispatch via draw_inspector callbacks — also fixes the latent CoaxCable/Equalizer empty-panel-title bug
• nodeKindFromLabel deleted; NodeGraphWidget::registerNodeKind/kindForLabel data-driven from registry
• New Component form combo from registry authorable rows

Phase 2 — PFBViewManager (new app/include/pfb_view_manager.h): owns the four lockstep PFB widget/visibility vectors; six hand-rolled rebuild sites collapse to method calls (issue #37 class of bug)

Phase 3 — ProjectSerializer (new app/include/project_serializer.h): .rfsim save/load/new JSON logic extracted; RfSimulatorApp methods become thin wrappers

Tests — new standalone exe tests/test_component_dispatch.cpp (MinGW TEST_CASE ceiling): Equalizer dirty-flag regression (red→green), all-11-types save/load round-trip, legacy .rfsim backward-compat load, registry label_prefix→kind mapping, draw_inspector/create completeness

Docs — DOX pass: app/AGENTS.md, common/AGENTS.md, openwiki/testing/guidance.md

Test plan

• cmake --build build — clean
• build/bin/tests.exe — 217 cases / 65522 assertions pass (incl. [project_file] round-trips)
• build/bin/test_component_dispatch.exe — 5 cases pass
• build/bin/test_ui.exe — 22/22 pass
• build/bin/test_issue37_pfb_input_removal.exe, test_component_authoring.exe, test_extensions.exe — pass
• bash scripts/format.sh --check — clean

Notes

• Backward compatible: .rfsim type strings and canvas menu labels byte-identical; library JSON schema untouched; legacy capitalized type names still load
• Known deferred minors (non-blocking, documented in branch): attenuator/amplifier deserialize clamp parity gaps (no current library file triggers them); PFBViewManager::draw() size-guard nit; dead includes in app.h; two openwiki/testing/guidance.md doc nits