Phase 2: enforce statement separators (Rule B)

The parser now requires a newline or ';' between statements (block() in
selfhost/parse.ludic); two statements may no longer sit adjacent with only
spaces. Also fixed if-without-else swallowing its trailing separator.

Migration: tools/ludic-tools/migrate_separators.c inserts ';' at statement
boundaries corpus-wide (examples, runtime, 25 self-host fragments, ~1100
boundaries). Verified semantically identical — the migrated compiler compiles
itself to IR byte-identical to the pre-migration seed, and every golden game
renders identically. Reseeded to the strict compiler; C-free fixpoint holds;
test.sh 14/14.

Docs: Rule B documented in LANGUAGE.md; BOOTSTRAP.md R1 + stale fences updated;
check-docs green across all docs. Fixed a multi-line string literal in
emit_expr.ludic (byte-identical \n escape) that the C toolchain lexer mis-lexes.

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

selfhost/buf.ludic

@@ -23,7 +23,7 @@ fn buf_putc(b: Buf, c: int) -> void {
 }
 fn buf_puts(b: Buf, s: ptr) -> void {
   let i = 0
-  while peek8(s, i) != 0 { buf_putc(b, peek8(s, i)) i = i + 1 }
+  while peek8(s, i) != 0 { buf_putc(b, peek8(s, i)); i = i + 1 }
 }
 fn buf_puti(b: Buf, n: int) -> void { buf_puts(b, itoa(n)) }
-fn buf_str(b: Buf) -> ptr { poke8(b.data, b.len, 0) return b.data }
+fn buf_str(b: Buf) -> ptr { poke8(b.data, b.len, 0); return b.data }