Add a .gitattributes linguist override so .rocky files render on GitHub

[hugocorreia90]

GitHub doesn't render .rocky files for syntax highlighting or count them in a repo's language statistics, because .rocky isn't a language Linguist recognizes. We can fix the display in this repo immediately with a .gitattributes override, without waiting on upstream Linguist.

Rescoped (2026-06-14): the original ask was to register a new Rocky language upstream in github-linguist. That's blocked: Linguist only accepts a new language once the extension reaches ~2000 files across a healthy distribution of distinct public repositories (CONTRIBUTING), which a brand-new DSL can't meet yet. Submitting that PR today would be rejected on the usage bar. This issue is rescoped to the in-repo override, which ships value now; the upstream submission is deferred until adoption clears the threshold.

Scope

Add a root .gitattributes that aliases .rocky to an existing Linguist language so the files render and count correctly in this repository:

*.rocky linguist-language=SQL linguist-detectable=true

(SQL is the closest existing grammar; pick whatever renders the DSL most legibly.) This is a per-repo display/stats override — it does not register a new "Rocky" language and does not affect any other repo.

Code refs

• New file: .gitattributes at repo root (none exists today)
• Linguist override docs: https://github.com/github-linguist/linguist/blob/main/docs/overrides.md
• .rocky sample files live in examples/playground/

Acceptance criteria

• .gitattributes added at repo root with a *.rocky linguist-language=… override
• After merge, .rocky files render with highlighting on GitHub and appear in the repo's language bar
• No other file types' detection changes

Effort

30 minutes.