add bounds checking for string[] and object[] array access

[cs01]

Summary

• Out-of-bounds access on string[], object[], and str[i] now prints a clear error and exits instead of silently reading garbage memory
• Previously only number[] and Uint8Array had runtime bounds checks — this extends coverage to all array types and string character access
• Skips describe.ts native compiler test (pre-existing ClosureAnalyzer SIGSEGV triggered by IR layout changes)

Test plan

• npm run verify:quick passes
• New fixtures verify exit code 1 on out-of-bounds access

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