docs(site): edit rules for clarity + cross-links; migrate off rules.txt

Editorial pass over site/ru/rules.md (on top of the verbatim port):
- moved the lore intro to the RU home page, rewritten in a modern voice;
- fixed typos, replaced the TODO/WTF cargo-tech note and the abandoned
  (---ссылка---) marker with the verified mechanic and a real cross-link,
  dropped the report TODO row;
- wove organic intra-page cross-links (#combat, #movement, #victory, ...);
- documented engine nuances verified against the code: ore auto-farming
  and the capital / "запасы промышленности" store (industry capped at
  population); cargo lost with ships destroyed in battle; and that a
  losing race's colonists at a neutral planet are NOT lost — they stay
  aboard (this corrects the audit note, verified in route.go).

Migration: delete game/rules.txt (its content now lives, authoritative,
in site/ru/rules.md) and repoint every reference to it (ui/frontend code
comments + tests, ui/docs, tools, ui/PLAN.md links). Record the
RU-authoritative rule in site/README.md and CLAUDE.md. The English
site/rules.md mirror follows in a separate stage.

ui/PLAN.md

@@ -1982,7 +1982,7 @@ Artifacts (Pass B — feature):
   preserves camera centre + zoom across route-driven remounts
   inside the same game id.
 - Topic doc `ui/docs/cargo-routes-ux.md` quotes
-  [`rules.txt`](../game/rules.txt) (lines 808–843) and maps
+  [`site/ru/rules.md`](../site/ru/rules.md) (lines 808–843) and maps
   semantics to UI; `ui/docs/renderer.md` documents the pick-mode
   contract; `ui/docs/calc-bridge.md` records the Phase 16 reach
   waiver (inline TS rather than a calc bridge for one
@@ -2075,7 +2075,7 @@ Artifacts:
   rewritten from the Phase 10 stub: empty form for the Create flow
   (name plus the five fields Drive, Armament, Weapons, Shields,
   Cargo) and read-only view + Delete affordance for an existing
-  class. Validation rules from [`rules.txt`](../game/rules.txt) live
+  class. Validation rules from [`site/ru/rules.md`](../site/ru/rules.md) live
   in `lib/util/ship-class-validation.ts` (TS port of
   `pkg/calc/validator.go.ValidateShipTypeValues`): each of drive /
   weapons / shields / cargo is 0 or ≥ 1; armament is a non-negative
@@ -2098,7 +2098,7 @@ Dependencies: Phase 14.
 Acceptance criteria:
 
 - the user can create, list, view, and delete ship classes;
-- field validation matches [`rules.txt`](../game/rules.txt)
+- field validation matches [`site/ru/rules.md`](../site/ru/rules.md)
   constraints with disabled Submit + tooltip when invalid;
 - double-tapping a row in the ship-classes table opens its
   designer (read-only view of the existing class);
@@ -2463,7 +2463,7 @@ Acceptance criteria:
 - the planet production picker (Phase 15) lists the user's sciences
   in the Research sub-row and lets the user select one for research
   production;
-- name validation matches [`rules.txt`](../game/rules.txt)
+- name validation matches [`site/ru/rules.md`](../site/ru/rules.md)
   constraints (length, allowed characters, special characters not
   at start/end, no triple repeats).
 
@@ -2563,7 +2563,7 @@ Targeted tests:
 Status: done (local-ci run 2).
 
 Goal: present every section of the current turn's report as readable
-panels, mirroring the structure documented in [`rules.txt`](../game/rules.txt) and
+panels, mirroring the structure documented in [`site/ru/rules.md`](../site/ru/rules.md) and
 `docs/FUNCTIONAL.md` §6.4.
 
 Artifacts: