refactor(stdlib): de-abbreviate namespaces (Mem/Sys/Net/Collide)

Expand the abbreviated public namespaces to full words, part of the
language-wide de-abbreviation pass:
  Mem -> Memory, Sys -> System, Net -> Network, Collide -> Collision

Math stays (universally accepted, like int/bool). Renames the dispatch
strings, LSP signatures, docs (dirs, files, frontmatter), and the
inventory manifest; behavior is byte-identical (the bare rt_ targets are
unchanged). Reseeded; C-free bootstrap fixpoint holds; all suites green.

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

docs/language/memory/memory-bytes.md

@@ -0,0 +1,14 @@
+---
+id: memory-bytes
+name: Memory.bytes
+category: memory
+kind: namespace-method
+tokens: Memory.bytes
+sig: Memory.bytes(n) -> ptr
+tip: Allocate n bytes.
+order: 0
+ns: Memory
+member: bytes
+---
+
+Allocates an <code>n</code>-byte buffer and returns a pointer to it.