repo code search: add filter controls that prefill the query (like /search) · Issue #4719 · tangled.org/core

On /search, clicking a language, author or sort option writes the matching key:value token into the search input.

On /{owner}/{repo}/search, the only guidance is the help text ("Narrow it with lang:go, file:readme, or case:yes"). Users must type the syntax themselves.

Proposal: add the same controls to repo search:

a language list (from the repo's language breakdown) → lang:<name>
a case:yes toggle
optionally, file: suggestions from the file index

Each control edits the query string, so the URL (?q=) stays the single source of truth and the page still works without JS.

Related: #612 (same idea for issue/PR filters), #4171 , #4558 .