docs(link): the player-vendor marketplace (Protocol 3.0 §8)

Documents order 5b across the four repos, and records what building it changed
about §8 as designed.

- NEW website/MARKETPLACE.md — the operator guide: what the pages must say out
  loud and why, the privacy contract (the player's in-game Vendor Search toggle
  wins, and no admin setting overrides it), the Bridge.cfg knobs and how they
  trade against each other, and the measured sweep costs.
- INTEGRATION.md — catalog entry for vendor.listing / vendor.listing.remove with
  its six consumer gotchas, and the GET /market REST section (the sidecar's only
  paged read, and why it orders by serial rather than shop name).
- BACKEND_DESIGN.md — shard_vendors / shard_vendor_items, the routes, and the
  marketplace search as the only rate-limited public read.
- SHARD_VISIBILITY.md — why the market's fields default to Everyone (the in-game
  gump already shows exactly that set), why location is one setting covering
  four things, and why hiding the owner name without the owner id achieves
  nothing.
- PLAN.md — the amortized round-robin as the one sweep pattern the bridge did not
  previously have, and an update to §7's cliloc note: pushing name resolution to
  the plugin was never an option, because ServUO cannot read a modern client's
  compressed cliloc files either.
- v3.md §8.8 — the four things the build settled differently, chief among them
  that §8.1's FLAT location payload would have made Part A's pre-wired
  market.location rule inert, exactly like the characterName miss one part
  earlier.

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

website/SHARD_VISIBILITY.md

@@ -60,12 +60,32 @@ board while holding back one column. See the table in §3.
 | **Shard rules** | Skill/stat caps, house limits, vet rewards, the ruleset | Everyone | Connect address → Everyone |
 | **Spawn atlas** | Bestiary and spawn locations (static content) | Everyone | — |
 | **Leaderboards** | Point and loyalty standings | Everyone | Character names → Everyone |
-| **Marketplace** | The shard-wide player-vendor index | Everyone, **live updates off** | Vendor owner name → Everyone · Location → Everyone |
+| **Marketplace** | The shard-wide player-vendor index | Everyone, **live updates off** | Vendor owner name → Everyone · Vendor owner character id → Everyone · In-game location → Everyone |
 
 **Why the marketplace ships with live updates off.** A live feed of every vendor's full inventory
 would be the single largest thing the site sends. No page needs it — the marketplace is a search over
 stored data with a “prices last refreshed N minutes ago” stamp. Turn it on only if you want it.
 
+**Why the marketplace's fields default to Everyone.** A vendor's shop name, its owner's character
+name and where it is standing are *already* visible to every player in game: the stock Vendor Search
+gump surfaces exactly that set to anyone who opens it. Publishing them on the site is not a new
+disclosure. They stay configurable because a shard may still prefer to keep its economy behind a
+login — and because "already public in game" is a judgement about your shard, not ours.
+
+**Location is one setting covering four things.** Hiding it removes the facet, the coordinates, the
+region *and* the house name together. That is deliberate: those are four ways of saying the same
+thing, and a setting that hid the coordinates while publishing the house name would not have hidden
+anything.
+
+**Hiding the owner name also hides the owner character id.** They are separate settings so you can
+be explicit, but leaving the id published while hiding the name achieves nothing — the leaderboards
+and guild boards resolve that same id back to a character name. Set both.
+
+**What hiding a vendor cannot do.** Only vendors whose owner left the in-game *Vendor Search* flag ON
+are ever sent to the site, so a player who hides their shop in game is hidden here too — and no
+setting on this page can override that. It works the other way as well: these settings control who
+sees the index, not whether players can find each other's shops in game.
+
 **Why house owner/price default to Staff.** The public Houses page has always been a "where are the
 falling houses" board — location only. Owner and price are the staff view. That split is preserved.