docs: DEPLOYMENT.md becomes docs/deployment.md, and gets published

It was the one reader-facing how-to living at the repo root, and that had a
consequence beyond tidiness: colliepwa.dev publishes the nine files the
README's documentation table lists, so every link to a front door other than
the default sent a reader off the site and into GitHub. Eight links, from the
pages most likely to need them.

Moved, listed in the table, and cut on the way: 621 lines to 380. Every
variant heading keeps its anchor, every COLLIE_* name and every code block
survives; what went is the rationale around them.

In-code pointers now name docs/deployment.md, including the two the operator
reads — the COLLIE_SKIP_SERVE warning in bridge/server.ts and doctor's serve
finding. cli/pack.ts keeps its old spelling for now: another session has
uncommitted work in that file.