Merge commit 'aad3f8c' into lang/foundations

changes/ui-override.md

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+bump: minor
+type: feature
+**`ui_override(path, text)`: a template or stylesheet given from outside.** From then on a read of `path` answers
+`text`; a component whose template or stylesheet it is swaps its own and is shown again with its state kept,
+and an importer reads the new text. `ui_override_clear(path)` (or `""` for every one) brings the file back,
+and `ui_overridden(path)` says whether one stands. A developer build's disk polling leaves an overridden
+component alone. For a studio editing a running game's interface (devlink's `ui_override`); a game that
+overrides nothing pays a length check per file read.