Result codes

Every reply lists what did not happen as asked. Each warning names the layer and the fix; the app shows the same warnings as badges on the canvas.

Code	Meaning
`INPUT_ALIASED`	note: a key or value was read in its canonical form
`INPUT_IGNORED`	a key was not understood and did nothing; fix the spelling it names
`NOT_APPLIED`	asked for X, got Y; change the request or the parent
`NOT_SUPPORTED`	the engine cannot do this yet; the rest of the call was applied
`LAYOUT_OVERFLOW`	content is clipped by a fixed-size frame
`EXPECT_FAILED`	a layer's expect (lines, fits, size, noOverlap) did not hold
`LAYOUT_OCCLUDED`	an edge-pinned bar or overlay covers content
`TEXT_TRUNCATED`	text does not fit its fixed box
`FONT_SUBSTITUTED`	a requested font family is not installed; another one draws the text
`TOKEN_FALLBACK`	a variable was not found; its fallback value was used
`OVERRIDE_UNMATCHED`	an instance override names no property or layer
`FONT_INSTALLED`	note: a font family missing on this machine was installed from Google Fonts for this host
`IMAGE_SOURCE`	note: where a fetched photo came from: title, author, license and page
`HISTORY_EMPTY`	note: undo or redo found nothing to step
`SCRIPT_LOG`	note: a line a script wrote with console.log
`SCRIPT_ERROR`	error: a script threw or ran out of time; everything it did was rolled back
`INVALID_INPUT`	error: nothing changed; the message says what to fix
`NOT_FOUND`	error: a node, component or variable does not exist
`FILE_NOT_FOUND`	error: a "file" argument names a file other than the one this host serves
`UNKNOWN_TOOL`	error: no tool has that name; the message suggests one
`ENGINE_ERROR`	error: the engine refused a step; nothing changed