docs(readme): Quick Start above the fold; add Glossary; pack repo link

[anthroos]

Why

UX audit findings on the engine README:

1. Quick Start was section 4 of 15 — buried under "The Question", "What It Is Not", and "The Methodological Core". A new visitor had to read three philosophy sections before seeing git clone.
2. Four overlapping terms used without definition — `trajectory`, `pack`, `skill`, `openexp-use`. Readers conflate them; the README never lays them out.
3. No bridge from Quick Start to a working demo — after `./setup.sh` finishes, a fresh visitor doesn't know what to do next. The seed pack lives in its own repo now (after refactor: split packs out of engine repo (one repo per pack) #14) but the README didn't point to it.

What

• Reorder: Quick Start moved directly after the hero. Order is now hero → Quick Start (with pointer to seed pack) → The Question → Glossary → What It Is Not → Methodology → How It Works → ...
• Add Glossary section — four terms, one line each. Resolves the trajectory / pack / skill / openexp-use confusion.
• Quick Start pointer to the seed pack — `exp-inbound-acquisition-with-free-pilot`. After setup.sh, fresh visitors have a concrete next step: install a real pack, try retrieval.

Diff

`README.md | 41 ++++++++++++++++++++++++++++--------------` — 27 insertions, 14 deletions, net +13.

Existing TOC anchors (`#quick-start`, `#how-it-works`, `#publishing-an-experience`) still resolve.

Test plan

• Confirm Quick Start renders before the philosophy sections
• Confirm seed-pack link in Quick Start opens `anthroos/exp-inbound-acquisition-with-free-pilot`
• Confirm Glossary anchors are accessible via section heading