feat: Bytecode v2 header for predicate support

[zharinov]

Summary

• Bytecode v2: compute section offsets from counts (removes 8 explicit offset fields)
• Add str_blob_size and regex_blob_size to header for blob storage
• Reserve has_predicate bit in Match instruction for text filtering
• Delete TypeMetaHeader (counts now in main header)

Why

Foundation for predicates — filtering nodes by text content:

(identifier == "foo")       ; exact match
(identifier ^= "get")       ; starts with
(identifier =~ /^test_/)    ; regex match

This PR prepares the bytecode format; parser/compiler/VM follow in separate PRs.