chore: upgrade to Zig 0.16.0-dev (master)

[lodekeeper-z]

Upgrade to Zig 0.16.0-dev (master) — part of the lodestar-z Zig master upgrade effort.

Key changes:

• std.io → std.Io migration
• std.Io.Dir methods now require explicit io parameter
• Build system changes for 0.16 compatibility

🤖 Generated with AI assistance

[wemeetagain]

@lodekeeper-z please refresh this PR based on the latest main branch

[lodekeeper-z]

Refreshed against latest main — merged in #10 (Ref refactor), #8 (raw variant functions), and #5 (safer callbacks). Updated the type_tag and hello_world examples to match the new wrap() signature (added ref parameter).

Note: the type_tag example has a linker issue (undefined NAPI symbols) that's pre-existing from upstream — it was introduced when #7 and #10 were merged without updating the example's wrap() call site. Our branch now fixes that compilation error, but the example still can't link standalone (needs to run as a Node addon).

[nazarhussain]

@lodekeeper-z please refresh this PR based on the latest main branch

[lodekeeper-z]

Refreshed — merged latest main (napi→zapi rename, CI workflows, type_tag example). hello_world example is still TODO due to std.time.Timer/std.Io migration in 0.16.

[lodekeeper-z]

Refreshed — merged latest main (napi→zapi rename, CI workflows, type_tag example). hello_world example is still TODO due to std.time.Timer/std.Io migration in 0.16.