avnd ui: resolve file-path templates before syncing them to custom items

[bltzr]

Problem

File-chooser port values are stored in the document as path templates (<PROJECT>:..., <LIBRARY>:..., or document-relative). Score's own file widgets resolve them through score::locateFilePath, but the avnd layout builder pushed the raw template string into custom UI items' value.

So an add-on widget bound to a soundfile/file/folder port received a path it cannot use — e.g. a waveform widget that decodes the file to display it in edit mode could never find <PROJECT>:samples/foo.wav. Values worked during execution only because the engine resolves paths on its own side, which made panels that depend on the path (waveform displays, folder pickers) appear empty until playback started.

Fix

Resolve through score::locateFilePath in LayoutBuilder::setupControl, both for the initial sync and in the valueChanged connections, whenever the inlet is a Process::FileChooserBase or Process::FolderChooser and the value is a non-empty string. Other value types and non-file ports are untouched.

Verified with an avnd add-on (Granola) whose custom waveform widget decodes the Sound port's file: with this change the widget receives /abs/path/samples/foo.wav at document load and can display the waveform in edit mode, matching the behavior of score's built-in file widgets.

🤖 Generated with Claude Code

https://claude.ai/code/session_01AvD2PFHZtW6pfsh3gGhayg

[bltzr]

I think this is the reason why Granola's sound file port would not load the waveform at scenario load.

[jcelerier]

arf, this is incurring the qobject_cast cost *2 on every widget creation, that's not great :/

[jcelerier]

the correct way here would be to do it statically: from avnd_port_type we know whether something is a file port, folder port, or something else. I'd add a separate "SetGUIValue" struct that follows the existing patterns for pattern-matching avendish port types at compile-time with concepts

[jcelerier]

This way instead of being done at run-time it is done 100% at compile-time

[bltzr]

Reworked as suggested (6446921): the runtime qobject_casts are gone — a SetGUIValue<T> customization now dispatches at compile time on the avnd port type, in the same concept-constrained-specialization style as ProcessModelPortInit.hpp. The file/folder specialization (avnd::soundfile_port || avnd::midifile_port || avnd::file_port || T::widget::folder — the exact set score gives FileChooser/FolderChooser inlets) applies score::locateFilePath; the primary template passes values through untouched. WidgetInlets.hpp include dropped from Layer.hpp.

One conscious delta: avnd::dynamic_ports aggregates take the pass-through path (the runtime cast would have matched their FileChooser inlet) — dynamic file-port lists bound whole into a custom ui item weren't a case this PR targeted, but flagging it for completeness.