Unexpected syntax errors in :hapi:generatePbjSource

Latest 'main' build:

https://github.com/hiero-ledger/hiero-consensus-node/actions/runs/19283530532/job/55139450487#step:23:557
```
> Task :hapi:generatePbjSource
line 9:9 mismatched input '"proto2"' expecting {'"proto3"', ''proto3''}
line 40:26 missing ':' at '{'
line 50:26 missing ':' at '{'
line 39:9 mismatched input '"proto2"' expecting {'"proto3"', ''proto3''}
line 60:13 mismatched input '536000000' expecting {'syntax', 'import', 'weak', 'public', 'package', 'option', 'repeated', 'oneof', 'map', 'int32', 'int64', 'uint32', 'uint64', 'sint32', 'sint64', 'fixed32', 'fixed64', 'sfixed32', 'sfixed64', 'bool', 'string', 'double', 'float', 'bytes', 'reserved', 'to', 'max', 'enum', 'message', 'service', 'rpc', 'stream', 'returns', BOOL_LIT, IDENTIFIER}
line 60:38 mismatched input '{' expecting INT_LIT
line 61:10 mismatched input ':' expecting {'syntax', 'import', 'weak', 'public', 'package', 'option', 'repeated', 'oneof', 'map', 'int32', 'int64', 'uint32', 'uint64', 'sint32', 'sint64', 'fixed32', 'fixed64', 'sfixed32', 'sfixed64', 'bool', 'string', 'double', 'float', 'bytes', 'reserved', 'to', 'max', 'enum', 'message', 'service', 'rpc', 'stream', 'returns', BOOL_LIT, IDENTIFIER}
line 62:8 mismatched input ':' expecting {'syntax', 'import', 'weak', 'public', 'package', 'option', 'repeated', 'oneof', 'map', 'int32', 'int64', 'uint32', 'uint64', 'sint32', 'sint64', 'fixed32', 'fixed64', 'sfixed32', 'sfixed64', 'bool', 'string', 'double', 'float', 'bytes', 'reserved', 'to', 'max', 'enum', 'message', 'service', 'rpc', 'stream', 'returns', BOOL_LIT, IDENTIFIER}
line 63:13 mismatched input ':' expecting {'syntax', 'import', 'weak', 'public', 'package', 'option', 'repeated', 'oneof', 'map', 'int32', 'int64', 'uint32', 'uint64', 'sint32', 'sint64', 'fixed32', 'fixed64', 'sfixed32', 'sfixed64', 'bool', 'string', 'double', 'float', 'bytes', 'reserved', 'to', 'max', 'enum', 'message', 'service', 'rpc', 'stream', 'returns', BOOL_LIT, IDENTIFIER}
line 44:17 extraneous input 'amount_micros' expecting '='
line 56:17 extraneous input 'amount_micros' expecting '='
line 60:18 extraneous input 'currency_code' expecting '='
line 67:18 extraneous input 'name' expecting '='
line 71:18 extraneous input 'value' expecting '='
ServiceGenerator Warning - Unknown element: [383 301 119] -- ;
ServiceGenerator Warning - Unknown element: [383 301 119] -- ;
ServiceGenerator Warning - Unknown element: [383 301 119] -- ;
```

Start with the linked GitHub Actions job and the :hapi:generatePbjSource task to identify which source inputs produce the reported parser errors. Determine the cause of the syntax and generator warnings, then verify that the task completes without these errors on the main build.

Written by the indexing model from the issue text.