chore(codegen): drop unused suffix forms digits_optional / any

Both forms came in with the codegen split (#91) but no [[vpn]]
rule has ever used them — the only `suffix=` rules are `digits`
(`wlan` test vector + `if` from #93). The grammar surface paid
for itself in ~150 lines of dead C/Rust helpers + their tests.

Drop them from VALID_KINDS, the parser, the C/Rust/Kotlin
emitters, and the helper test cases. If a future rule needs
either form, reintroduce alongside the rule that needs it.

Re-ran the codegen; tests pass for all four targets.

data/interfaces.toml

@@ -13,8 +13,6 @@
 #   { exact   = "lo"     }                          name == "lo"
 #   { prefix  = "rmnet"  }                          name.starts_with("rmnet")
 #   { prefix  = "wlan", suffix = "digits" }         starts_with + rest is 1+ ASCII digits
-#   { prefix  = "seth_lte", suffix = "digits_optional" }  starts_with + rest is 0+ ASCII digits
-#   { prefix  = "v4-", suffix = "any" }             starts_with + rest is 1+ any chars
 #   { contains = "vpn"   }                          needle anywhere in name
 #
 # All matches are ASCII case-insensitive.