feat(lang): #76 namespace block form with export/internal visibility

`namespace Name { export function foo(...) ... internal function bar(...) ... }`
declares a Name.* namespace once and controls its public surface declaratively,
instead of annotating every function with @Namespace(Name). Inside the block
each `function short(...)` is emitted as `namelower_short`; export (the default)
makes it callable as Name.short(...), internal keeps it a private helper
(emitted, callable by short name from siblings — calls are rewritten — but
Name.internalOne() is a compile error). Block sugar for the per-function
@Namespace annotation; a package's public API reads at a glance. Namespaces
declared the old way are unchanged (gameplay_foundation still passes).

namespace added to LUDIC_KW_DECL + JetBrains/TextMate + docs page + inventory
(vocab/impl/docs checks green). Example namespace_block (export + internal +
sibling calls + internal-visibility compile error verified). Full suite 116/0,
fixpoint holds.

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

tools/ludic-tools/ludic_syntax.h

@@ -52,7 +52,7 @@ typedef struct {
  * mirror the compiler's parser: anything parse_decl() dispatches on is a
  * declaration keyword, anything stmt() dispatches on is a statement keyword. */
 static const char* LUDIC_KW_DECL[] = {
-    "program","import","property","model","enum","ui",
+    "program","import","property","model","enum","ui","namespace",
     "const","var","function","extern","handler","entry","event","scene","test", 0
 };
 static const char* LUDIC_KW_CLAUSE[] = {