OfficeArt reader

RecursiveAI.OneDocument.OfficeArt reads the drawing layer ([MS-ODRAW]) that the binary Word, Excel and PowerPoint formats share. It is a record-level reader: it finds, bounds and decodes records and leaves their host-specific meaning to the format that embeds them.

• Records. ArtRecords.Parse turns bytes into ArtRecord trees. A record header is eight bytes (recVer 4 bits, recInstance 12, recType 16, recLen 32); recVer 0xF marks a container. The PowerPoint binary format uses the same header, so the parser serves its own record stream too. A record that claims more bytes than remain is clamped and reported; the record count, record size and nesting depth limits of OfficeLimits apply. Every record keeps its raw bytes as a slice of the parsed buffer, so unknown records are carried without copying.
• Drawings. ArtDrawing.Parse reads a drawing container into the patriarch group, nested groups and shapes (ArtShape): shape id, type (MSOSPT), flags, merged property tables, group coordinate space, child anchor, and the host records (ClientAnchor, ClientData, ClientTextbox) as raw records.
• Properties. ArtProperties merges the primary, secondary and tertiary tables. Boolean sets are read with GetFlag(set, flag, default), which honours the "use" bit 16 positions above each flag. Colours are ArtColor (RGB bytes plus the flag byte; the scheme-index flag is for the host to resolve). Complex properties are slices; GetString and GetArray decode UTF-16 text and IMsoArray.
• Pictures. ArtDrawingGroup.Parse reads the group and its BLIP store; ArtBlipStore.GetImage returns the picture of a one-based index, reading it from the delay stream (Pictures in PowerPoint files) when it is not embedded. Metafile data is inflated within MaxAllocationBytes; a DIB gets a BMP file header; JPEG, PNG and TIFF bytes are returned as stored.
• Defects. The art. codes in defects.md.