Phase 6b: a handler's query is @Queries only; drop the signature clauses

The handler-signature `query (vars) [terms] where …` clause and the
`reads`/`writes` clauses overlapped the `@Queries` annotation (and each other):
two ways to attach a query to a handler. Consolidated on the decorator.

  - parse_system no longer parses `query`/`reads`/`writes` clauses; it keeps the
    postfix `@anno(...)` channel and `phase`. A handler's query is the prefix
    `@Queries(these: [...], on: Model)` annotation. Data-access hints are now
    `@Reads(...)`/`@Writes(...)` — absorbed by the generic annotation skipper,
    same parse-and-reserve status the old clauses had.
  - The inline `for (…) in query […] where …` statement is unchanged and still
    covers cross-property constraints / multiple kind filters. `query` stays a
    keyword there (now dispatched via is_id so the vocabulary check sees it).

examples/hello.ludic and examples/qdecl.ludic migrated to `@Queries` (qdecl now
demonstrates a per-property constraint + `on:` tag); outputs unchanged
(4 4 10 3 / 0 3 -2). LANGUAGE.md handler sections rewritten. Vocabulary: drop
`reads`/`writes` from CLAUSE (ludic_syntax.h, grammar, LudicTokens.kt).

Reseeded (21931 lines); C-free fixpoint holds; goldens identical; 17/17;
vocab + doc-fences clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/hello.ludic

@@ -15,13 +15,12 @@ program Hello {
     }
   }
 
-  # a system can declare the entities it operates on: the body then runs once
-  # per match, with the components bound and self() giving that entity.
-  handler Move phase FixedUpdate
-    query (p, v) [Pos, Vel]
-  {
-    p.x = p.x + v.dx
-    p.y = p.y + v.dy
+  # a handler declares the entities it operates on with @Queries: the body then
+  # runs once per match, each property bound by name and self() giving that entity.
+  @Queries(these: [Pos, Vel])
+  handler Move phase FixedUpdate {
+    Pos.x = Pos.x + Vel.dx
+    Pos.y = Pos.y + Vel.dy
   }
 
   handler Report phase Update {

examples/qdecl.ludic

@@ -1,13 +1,13 @@
 # ============================================================================
-# qdecl.ludic — a system whose query lives in its signature.
+# qdecl.ludic — a handler whose query lives in a @Queries annotation.
 #
-#   system CleanBattle phase LateUpdate
-#     query (b, p) [Battle, Pos, {Foe}] where b.hp <= 0
-#   { … }
+#   @Queries(these: [Battle{hp <= 0 and side == 1}, Pos], on: Foe)
+#   handler CleanBattle phase LateUpdate { … }
 #
-# is the same thing as writing `for (b, p) in query [...] where ... { … }` around
-# the whole body — the loop header just moves into the declaration. The body runs
-# once per matching entity, and self() is that entity.
+# is the same thing as writing `for (Battle, Pos) in query [Battle, Pos, {Foe}]
+# where Battle.hp <= 0 and Battle.side == 1 { … }` around the whole body — the
+# loop header moves into the annotation. Each property binds by name, the body
+# runs once per matching entity, and self() is that entity.
 # ============================================================================
 program QueryDecl {
   property Battle { hp: int = 0, side: int = 0 }
@@ -20,17 +20,17 @@ program QueryDecl {
     spawn Foe { Battle { hp: -2, side: 0 } }
   }
 
-  handler CleanBattle phase LateUpdate
-    query (b, p) [Battle, Pos, {Foe}] where b.hp <= 0 and b.side == 1
-  {
-    print_int(p.x)
+  # a per-property constraint `Battle{...}` qualifies its bare fields to that
+  # property; `on: Foe` adds the {Foe} kind filter.
+  @Queries(these: [Battle{hp <= 0 and side == 1}, Pos], on: Foe)
+  handler CleanBattle phase LateUpdate {
+    print_int(Pos.x)
     despawn self()
   }
 
-  handler Census phase Render
-    query (b) [Battle]
-  {
-    print_int(b.hp)
+  @Queries(these: [Battle])
+  handler Census phase Render {
+    print_int(Battle.hp)
   }
 
   handler Bye phase Render { quit() }