MODERNIZE.md

In a subagent per implementation, list (don't apply) code that could use newer idioms — but nothing that:

• adds ternaries/switch/match (only Cell#to_char), endless/expression bodies, or combined/flattened ifs
• changes make_key's key local, Odin param groups, C/C++ auto, F# <> null, or unless minimal on its own line
• removes commented-out-code imports (grep first), tuple/Pair DIRECTIONS, existing, _f, Play/World/Cell, or Kotlin public
• breaks add_cell→bool, optional next_state, or the active "fastest" variant
• reformats untouched code, drops struct trailing commas, or skips updating commented render/alive_neighbours variants (see AGENTS.md/IMPLEMENTATION.md)

Won't compile / not an improvement — don't propose:

• AssemblyScript: no Map get-or-null (Map.getOrNull); unsigned cast breaks the negative-offset bounds check (<u32>dir[0]).
• Ballerina: no ?? null-coalescing (x ?? false); += doesn't preserve int:Unsigned32 (self.tick += 1).
• Fortran: pure only works on make_key (pure function cell_at).
• Groovy: no for-header destructuring (for ((rel_x, rel_y) in DIRECTIONS)).
• Inko: can't call an ownership-taking method on a borrowed field (cell.next_state.or(false)).
• Kotlin: no native fixed-precision float formatting (String.format("%.3f", ...)).
• Navi: no for-header destructuring (for (let [rel_x, rel_y] in DIRECTIONS)).
• OCaml: Random.self_init not deprecated.
• Odin: or_else needs the .? assertion (next_state or_else false).
• Perl: n-at-a-time foreach doesn't fit list-of-pairs DIRECTIONS (foreach my ($rel_x, $rel_y) (...)).
• Pony: no optional shorthand (Bool?); named args need where; no += (x += 1).
• SQL: SQLite generate_series rejects a column alias (generate_series(...) AS gx(value)).
• V: no os env-presence check (os.is_env_set); optional map lookup needs or {}; no infinity literal (math.inf(1)).
• Zig: can't bit-cast i96 to 64-bit (@bitCast to u64).