add help docs and ?

docs/nodes/Font.md

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+# Font
+
+Build a reusable font specification for annotation overlays. Choose a discovered system font, use the default fallback stack, or point to a custom font file.
+
+## Inputs
+
+None.
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| font | FONT | Font specification for use with Annotations and similar nodes |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| family | dropdown | System default | Font family name; includes discovered system fonts plus "Custom file" option |
+| font_file | FILE_PICKER | "" | Path to a custom font file; visible only when family is set to "Custom file" |
+
+## Limitations
+
+- Custom font files must be in a format supported by the underlying font rendering library (e.g. TTF, OTF).
+- System fonts are enumerated at startup; newly installed fonts require restarting the application.