fix(publisher): validate JSON encoding before publishing to catch Windows codepage corruption

[hiro-nikaitou]

Summary

On Windows systems running under Git Bash/MSYS with a non-UTF-8 ANSI codepage (e.g. zh-CN CP-936/GBK), UTF-8 bytes in server.json description fields can be silently reinterpreted through the system codepage. The result is corrupted metadata in the registry containing lone surrogate characters (e.g. \udc94).

This adds a validatePublishData() function that checks both valid UTF-8 encoding and absence of JSON-escaped lone surrogates (\udc00-\udfff) before transmitting the publish or validate request. If corruption is detected, the command fails with a clear error message suggesting running from PowerShell or CMD instead of Git Bash.

Changes

• publish.go: Added validatePublishData() function and call before HTTP send
• validate.go: Added validatePublishData() call in validateViaAPI for consistency
• publish_internal_test.go: 9 test cases covering valid ASCII, UTF-8 Unicode, invalid UTF-8, lone surrogate detection (lowercase, uppercase, end range), and false-positive avoidance

Testing

• go build ./cmd/publisher/... passes
• go vet ./cmd/publisher/commands/ passes
• All 9 validation unit tests pass
• Existing publish integration tests pass

Fixes #1306

[rdimitrov]

Hey, @hiro-nikaitou, thanks for the contribution but there was another PR already opened (#1310) and it was fair to go with it! Anyway, the issue is now addressed so with the next release it would be available to everyone! Thanks again!