fix(pptx): render shape image fills, fix picture placeholders, and load embedded fonts

[karthikmudunuri]

Summary

Fixes a set of PPTX import-rendering fidelity gaps surfaced by a real-world deck (an "Education" template). Each was verified against the actual file; the font work was additionally verified in real headless Chrome (the browser's OTS sanitizer is far stricter than fontTools).

1. Picture / SVG fills on shapes

Shapes whose fill is an <a:blipFill> — the modern Office "icon" pattern, including dual PNG+SVG blips — now render their artwork. Previously these custGeom icons (globes, stars, grid textures, brand marks) imported with no fill and showed blank/grey.

• Importer resolves the blip (prefers the sharper SVG embed) to a url("data:…") and feeds it into the existing fill field.
• ShapeView paints the image clipped to the custGeom silhouette, or as a box-filling background for rect/rounded/circle.

2. Picture-placeholder handling

• Empty picture placeholders inherited from the layout no longer leak onto the slide as grey "Insert Picture" prompt boxes.
• Picture placeholders the slide hosts now inherit their rounded geometry + fill from the layout/master placeholder, so they render as the template intends.

3. Embedded fonts (EOT / MicroType-Express) now load

Embedded .fntdata fonts decode to browser-valid TTFs. Two independent bugs caused the browser's font sanitizer (OTS) to reject the whole font and fall back to a system typeface:

• Composite glyphs carrying WE_HAVE_INSTRUCTIONS on a non-first component produced a malformed glyf table (a parser read a non-existent instructionLength past the glyph).
• Format-12 cmap subtables shipped a non-zero language field (1007); OTS requires 0 on non-Macintosh platforms.

4. Weight-named font families

Weight-named embedded families (e.g. Montserrat Bold, Montserrat Semi-Bold) are now aliased to their base family at the matching numeric weight, so bold/semibold text bound to the base family uses the real embedded face instead of a synthetic bold. Display-only — deck.fonts (PPTX export) is untouched.

Verification

• All 8 embedded fonts load in headless Chrome with zero OTS errors (font1…font8 = true); base-family weights (Montserrat 400/600/700) resolve to the real faces.
• New tests: image-fill rendering (3), CTF composite reconstruction, cmap language sanitization, splitFamilyWeight (3 cases).
• Full slidewise suite: 70 passed, 9 pre-existing skips. Monorepo typecheck: clean.

Notes

• Export/round-trip is unaffected: shape source XML is preserved, and the weight aliasing is display-only.
• Line-height (1.2) was investigated and intentionally left unchanged — the observed title-overlap was caused by fallback-font width, not line spacing.