feat(examples): rotate example deck collection

Swap the example library — remove 14 older decks (early demos, consulting
samples that became repetitive once the catalog grew) and add 8 new ones
covering recently-developed visual paradigms: Memphis pop, Swiss
typographic grid, glassmorphism SaaS, risograph zine, ink-wash editorial,
Bloomberg data-journalism, architecture-photography editorial, and an
urban-renewal magazine feature.

Strip sources/ from every example — examples should be visual references
for the rendering pipeline, not source-document archives. Document the
omission in examples/README.md.

Simplify examples/README.md from ~500 lines to 40 — examples.json is the
canonical catalog (powers the online preview at hugohe3.github.io/ppt-master);
the README's per-project tables were duplicate worse-format data that
needed manual upkeep on every catalog change.

Downsize raster source images to <= 1280px longest side (slides are
1280x720, so anything larger was wasted bits). Regenerate svg_final/ and
exports/<slug>.pptx for each new deck so downloadable artifacts reflect
the shrunk source images.

Net effect on examples/: 718M → 528M (-190M, -26%); average new-deck
pptx halved (cangzhuo 22M → 7.9M, indie_bookstore 35M → 17M, etc.).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: hugohe3