Fix 500 when searching commit messages with non-ASCII terms

What does this MR do and why?

Searching commit messages on the new commit list with any non-ASCII term (Korean, Chinese, emoji, accented Latin) raised Encoding::UndefinedConversionError and returned a 500 (the frontend showed Unexpected token '<' ... is not valid JSON). In lib/gitlab/gitaly_client/commit_service.rb#list_commits, commit_message_patterns is a protobuf bytes field, but patterns were appended without encode_binary — unlike the adjacent author/path params.

This MR encodes each pattern as binary (one-line change) and adds a regression spec. encode_binary only relabels the encoding without changing bytes, so Gitaly still receives raw UTF-8 and matches correctly; ASCII behavior is unchanged.

Error details

Encoding::UndefinedConversionError
message : U+D5C8(허) from UTF-8 to ASCII-8BIT
lib/gitlab/gitaly_client/commit_service.rb:341:in `+'
lib/gitlab/gitaly_client/commit_service.rb:341:in `list_commits'
app/graphql/resolvers/repositories/commits_resolver.rb:45:in `resolve_with_lookahead'

References

• Resolves #621385 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Seed commits with non-ASCII messages in any local project:

   git clone <your-gdk-project> && cd <project>
   git switch -c unicode-fun
   git commit --allow-empty -m "허용된 커밋만 커밋하세요"
   git commit --allow-empty -m "修复了一个不存在的bug"
   git commit --allow-empty -m "🔥🔥🔥 hotfix: everything is fine 🔥🔥🔥"
   git commit --allow-empty -m "Ĥéllö Wörld: ûnicode åll thé wáy"
   git push -u origin unicode-fun

2. Visit the project's commit list at /-/commits/unicode-fun.

3. Filter by message with each term below. On master each raised a 500; with this MR they return the seeded commit (or an empty state) without error.

   Test cases

   Search term	Covers	Expected
   허용	Korean (customer repro)	1 result, no error
   不存在	Chinese	1 result, no error
   🔥	4-byte emoji	1 result, no error
   Wörld	accented Latin	1 result, no error
   Initial commit	ASCII regression check	unchanged behavior
   zzzz없음zzzz	non-ASCII with no matches	empty state, no error

4. Alternatively, from the rails console:

   repo = Project.find_by_full_path('<group>/<project>').repository
   repo.list_commits(ref: 'unicode-fun', query: '허용').commits.map(&:message)
   # before: Encoding::UndefinedConversionError — after: ["허용된 커밋만 커밋하세요"]

The regression spec fails on the unfixed code with the exact production error and passes with the fix.

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