BUGFIX: Move OWNERS to .github/CODEOWNERS to fix #3978

[chicks-net]

Summary

Fixes #3978

GitHub requires the CODEOWNERS file to be located in the .github/ directory (or repository root with that exact name) to function properly. This PR moves OWNERS to .github/CODEOWNERS and updates all references throughout the codebase.

Changes Made

• Renamed OWNERS → .github/CODEOWNERS
• Updated .gitattributes to reference the new location
• Updated build/generate/ownersFile.go to generate the file in the correct location
• Updated documentation in writing-providers.md to reference CODEOWNERS
• Added Tim as global owner

Test Plan

• Ran /bin/generate-all.sh to verify the generator creates the file in the new location
• Verified all file references were updated
• Checked that the file move preserves all content

% git grep OWNERS
.gitattributes:.github/CODEOWNERS eol=lf
build/generate/ownersFile.go:   file, err := os.Create(".github/CODEOWNERS")
documentation/advanced-features/writing-providers.md:  * `CODEOWNERS`

🤖 Generated with Claude Code

[tlimoncelli]

Hello friend!

Github is complaining that the people in CODEOWNERS do not have write permission. Each one gets an error such as:

Unknown owner on line 31: make sure @juliusrickert exists and has write access to the repository
providers/hostingde @juliusrickert

They don't have write permission because the current policy (from my employer) is that I have to approve any merge to main. Is there some other way to comply with the policy but give people write access?

[chicks-net]

Hello friend!

Howdy sir! 🙇

Github is complaining that the people in CODEOWNERS do not have write permission. Each one gets an error such as:

Unknown owner on line 31: make sure @juliusrickert exists and has write access to the repository
providers/hostingde @juliusrickert

They don't have write permission because the current policy (from my employer) is that I have to approve any merge to main. Is there some other way to comply with the policy but give people write access?

Oh dear, github policy and stackexchange policy are not playing nicely together here. 😭 Changing the policies is not a practical option. Effectively this means that the CODEOWNERS features won't work for us. I've given this some thought and research and suggest:

1. Going ahead with the rename to CODEOWNERS is moving things in a more correct direction even if it isn't going to do much for us as-is.
2. We should probably add in a comment to the generated CODEOWNERS file indicating the policy limitation.
3. The hoped-for functionality can be regained with https://github.com/marketplace/actions/assign-reviewers if we want to stick with CODEOWNERS format for the config or https://github.com/marketplace/actions/auto-request-review if we want to generate a new format too.

Would adding the comment be enough to make this PR worth landing? I'm happy to work on the other github actions in this PR or a new one.