refactor(codegen): widen VariableAllocatorContext with typeOf + resolveExpressionTypeRich

[cs01]

Adds typeOf + resolveExpressionTypeRich to VariableAllocatorContext so future migrations in variable-allocator.ts can opt in. No behavior change. The actual per-declaration call stays on flat resolveExpressionType pending investigation of a native-vs-node codegen divergence exposed when swapping (see task #45 notes).

[github-actions]

Benchmark Results (Linux x86-64)

Benchmark	C	ChadScript	Go	Node	Place
Cold Start	0.9ms	0.7ms	0.9ms	21.5ms	🥇
Hash Map Lookup	0.077s	0.059s	0.072s	0.095s	🥇
Binary Trees	1.107s	0.971s	2.061s	0.963s	🥈
Fibonacci	0.705s	0.707s	1.341s	2.620s	🥈
File I/O	0.074s	0.080s	0.082s	0.141s	🥈
JSON Parse/Stringify	0.028s	0.041s	0.123s	0.099s	🥈
Monte Carlo Pi	0.341s	0.348s	0.355s	2.014s	🥈
N-Body Simulation	1.382s	1.746s	1.776s	1.878s	🥈
Regex Match	0.013s	0.004s	0.017s	0.003s	🥈
SQLite	0.031s	0.266s	0.342s	0.320s	🥈
Quicksort	0.190s	0.218s	0.188s	0.225s	🥉
Sieve of Eratosthenes	0.011s	0.021s	0.016s	0.033s	🥉
String Manipulation	0.006s	0.014s	0.013s	0.031s	🥉
Matrix Multiply	0.396s	0.552s	0.410s	0.335s	#4

CLI Tool Benchmarks

Benchmark	ChadScript	grep	node	xxd	Place
Hex Dump	0.476s	—	0.793s	0.108s	🥈
Recursive Grep	0.018s	0.009s	0.084s	—	🥈