feat: preserve StringReference view navigation

[tinysec]

Summary

• retain the owning BinaryView on every core-produced StringReference
• expose official-style View, Raw, Value, and string conversion navigation
• propagate the view through Strings, StringReferences, range/address lookups, and ASCII detection
• centralize StringType decoding while preserving legacy GetRaw/GetValue overloads

Verification

• release build: 0 warnings, 0 errors
• external E2E: 113/113 passing
• official Python truth: 1,320 strings across cat, ls, and true with exact type/address/length/raw/value comparisons
• deterministic gzip truth snapshots reproduced byte-for-byte