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>

changes/namespace-block.md

@@ -0,0 +1,3 @@
+bump: minor
+type: feat
+Namespace block form (#76) — `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)` one at a time. Inside the block each `function short(…)` is emitted as `namelower_short`; an `export` function (the default) is callable as `Name.short(…)`, while an `internal` function is a private helper — emitted and callable by its short name from siblings in the block (calls are rewritten to the emitted name), but not part of the `Name.*` surface (`Name.internalOne()` is a compile error). It is the block sugar for the per-function `@Namespace` annotation, so a package's public API reads at a glance. A namespace declared the old per-function way is unchanged. Example: `examples/library/namespace_block.ludic`.