fix(json): JSON.parse<T> with 'any'-typed field stores raw JSON substring

[cs01]

Summary

Closes dapweb NOTES #12. any-typed fields inside a JSON.parse interface previously emitted @parse_json_any — broken IR with 'use of undefined type named any'. Now the parser serializes the JSON value's source text back to a string via csyyjson_val_write and stores it in the struct slot as i8*.

Why this is useful, not a hack

This is exactly the semantics for polymorphic payload dispatch (DAP, JSON-RPC, webhooks):

interface Envelope { command: string; body: any; }
const e = JSON.parse<Envelope>(rawWire);
switch (e.command) {
  case "launch": {
    const args = JSON.parse<LaunchArgs>(e.body);  // re-parse raw substring
    runLaunch(args);
    break;
  }
  case "setBreakpoints": {
    const args = JSON.parse<SetBreakpointsArgs>(e.body);
    ...
  }
}

dapweb was doing this manually with an extractField() walker — now it's native, zero boilerplate.

Scope note

any remains rejected as a parameter type (#5 behavior unchanged). This PR only addresses the interface-field case, where the field type maps to i8* anyway — the parser was just missing the generation branch.

Test plan

• New fixture tests/fixtures/builtins/json-parse-any-field.ts covers full envelope-dispatch pattern
• CI green

[github-actions]

Benchmark Results (Linux x86-64)

Benchmark	C	ChadScript	Go	Node	Place
Binary Trees	1.335s	1.215s	2.695s	1.139s	🥈
Cold Start	0.9ms	0.8ms	1.2ms	25.5ms	🥇
Fibonacci	0.815s	0.680s	1.572s	3.189s	🥇
File I/O	0.118s	0.099s	0.086s	0.202s	🥈
JSON Parse/Stringify	0.004s	0.005s	0.017s	0.014s	🥈
Matrix Multiply	0.448s	0.686s	0.557s	0.371s	#4
Monte Carlo Pi	0.388s	0.410s	0.405s	2.248s	🥉
N-Body Simulation	1.671s	2.118s	2.196s	2.387s	🥈
Quicksort	0.215s	0.244s	0.212s	0.261s	🥉
SQLite	0.354s	0.367s	—	0.415s	🥈
Sieve of Eratosthenes	0.013s	0.024s	0.018s	0.038s	🥉
String Manipulation	0.008s	0.018s	0.017s	0.036s	🥉

CLI Tool Benchmarks

Benchmark	ChadScript	grep	node	xxd	Place
Hex Dump	0.564s	—	0.952s	0.129s	🥈
Recursive Grep	0.019s	0.009s	0.099s	—	🥈