fix: native compiler segfault on unknown new expression at module scope

[cs01]

User impact

Before this PR, const x = new UnknownClass() at module scope caused the native self-hosted compiler (.build/chad) to segfault silently. After this PR, it emits a compile error and exits cleanly.

Root cause

VariableDeclaration creation sites had inconsistent field counts across parsers:

• 4-field sites (destructuring): { type, kind, name, value }
• 5-field sites (normal): { type, kind, name, value, declaredType }
• 6-field sites (statements.ts): { type, kind, name, value, declaredType, loc }

Per CLAUDE.md rule #3, the native compiler infers struct layouts from creation sites. Inconsistent field sets caused GEP misalignment — reading stmt.value returned a wrong pointer, and subsequent field accesses on the misaligned expression struct crashed.

Fix

1. Aligned ALL VariableDeclaration creation sites to include all 6 fields (adding declaredType: undefined, loc: undefined where missing)
2. Changed the inline type assertion in generateGlobalVariableDeclarations to use the real VariableDeclaration type (per rule Add cross compilation support #5: never invent subset types for assertions)

What this does NOT fix

• new Date() at module scope still segfaults — requires aligning NewNode creation sites, but doing so shifts the overall union struct layout and undoes the VariableDeclaration fix (cascading struct-layout interference)
• instanceof with class hierarchies still segfaults — same systemic issue
• These need a deeper fix: making the native compiler unify struct layouts from interface definitions rather than creation sites

Test plan

• tests/fixtures/edge-cases/new-unknown-class-module-scope.ts — new fixture
• npm run verify:quick — all tests + stage 1 self-hosting pass

[github-actions]

Benchmark Results (Linux x86-64)

Benchmark	C	ChadScript	Go	Node	Place
Binary Trees	1.572s	1.276s	2.691s	1.282s	🥇
Cold Start	1.0ms	0.9ms	1.3ms	31.3ms	🥇
Fibonacci	0.911s	0.794s	1.733s	3.367s	🥇
File I/O	0.087s	0.092s	0.086s	0.171s	🥉
JSON Parse/Stringify	0.004s	0.006s	0.016s	0.015s	🥈
Matrix Multiply	0.503s	0.665s	0.530s	0.479s	#4
Monte Carlo Pi	0.440s	0.439s	0.457s	2.591s	🥇
N-Body Simulation	1.748s	2.254s	2.290s	2.403s	🥈
Quicksort	0.246s	0.283s	0.242s	0.290s	🥉
SQLite	0.326s	0.342s	—	0.430s	🥈
Sieve of Eratosthenes	0.014s	0.027s	0.020s	0.042s	🥉
String Manipulation	0.008s	0.019s	0.016s	0.038s	🥉

CLI Tool Benchmarks

Benchmark	ChadScript	grep	node	xxd	Place
Hex Dump	0.446s	—	1.043s	0.139s	🥈
Recursive Grep	0.021s	0.011s	0.101s	—	🥈