[bobsingor]

A registered font's /BaseFont was the family it was registered under, with the spaces removed, so every weight of a family was written under one name: Noto Sans Hebrew Regular and Bold were both NotoSansHebrew. ISO 32000-2 9.6.3 and 9.7.4 make /BaseFont the font's PostScript name, and every other writer gives each weight its own (Acrobat's MinionPro-Regular, Word's Calibri-Bold, Chrome's Inter-SemiBold, WeasyPrint, pdfTeX, Quartz, PDFTron).

Readers that name fonts by it saw one font for two:

• Acrobat's Document Properties > Fonts lists one NotoSansHebrew (Embedded Subset) for a file with both weights; with the bold one renamed, it lists both.
• The engine's font list merged them into one 400-weight entry, so a bold box read back under the regular font's name in an engine that doesn't have the font registered.

The drawing was never wrong: each box points at its own embedded program.

What changes

• /BaseFont is the program's own name: its PostScript name, else Family,Style as a TrueType font without one is named. The family stays the descriptor's /FontFamily, which is what reopening resolves a registered font by, so finding it again doesn't change. EPDFFont_GetPostScriptName() reports the same name, as its header already promised.
• A variable-font instance is named as the font names that instance. Registration instances a variable font and keeps its name table, whose name 6 is the default instance's: a bold Roboto was named Roboto-Regular. Following Adobe Technical Note #5902, an instance takes its named instance's own PostScript name (RobotoRoman-Bold); else the family prefix and the instance's style (NotoSans-Bold); else the prefix and the weight (NotoSans_450wght).
• The subset tag hashes the program as well as its glyphs. Two weights number their glyphs alike, so the same text gave them the same tag; different subsets in one file now get different tags (9.6.4).

Files written before this keep their names until a box is edited and its appearance rewritten; nothing that finds fonts depends on the old names.

Tests

• TwoWeightsOfOneFamilyAreTwoFontsByName: Arimo Regular and Bold registered under one family give two names, two tags and one /FontFamily.
• VariableFontInstanceWithoutItsOwnName: a Noto Sans instance at 700 is NotoSans-Bold, one at 450 NotoSans_450wght.
• VariableFontIsInstancedAtRegistration checks the instance names; NoSubsettingFontEmbedsWholeProgram and RegisteredCffFontEmitsCidFontType0 now expect the PostScript name rather than the registered family.
• Each mutation fails its tests: the family name back, instances keeping name 6, a tag of the glyphs alone.
• Full macOS embedder suite: 1750 pass; the 12 failures are render and golden tests that fail the same way on embedpdf/main.
• Layer mode: the new test that writes is in the writers list; check-fork-tags --strict passes (the fork's own files).

With #101 merged in locally, both engines pass the font and mixed-script suites, and a file reopened without the fonts reads the bold box as NotoSansHebrew-Bold and lists two fonts. Meant to be released together with #101, so embedpdf pins once.