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>

tools/editors/jetbrains/src/main/kotlin/io/ludic/ide/LudicTokens.kt

@@ -45,7 +45,7 @@ object LudicVocabulary {
         "const", "var", "fn", "extern", "handler", "entry"
     )
     val CLAUSE = setOf(
-        "phase", "query", "reads", "writes", "on"
+        "phase", "query", "on"
     )
     val STMT = setOf(
         "let", "return", "if", "else", "while", "for", "in", "spawn", "despawn",