Instruction file imported from FrankZhaoYX/kdb_front_end_prototype_project (.github/instructions/frontend.instructions.md). Copyright stays with the author.

Front-end conventions

• No framework, no build step, no package.json. Plain HTML/CSS/JS only — keep it that way; this is a deliberate lightweight-stack decision, not an oversight.
• The report picker and the selected report's parameters live in one control bar at the top of the page: Category dropdown → Report dropdown (filtered by category) → that report's parameter fields, all in the same horizontal row, with results taking the full width below. Don't reintroduce a separate sidebar for parameters — that layout was tried and explicitly replaced.
• Parameter fields are generated dynamically from GET /api/reports/{id} — specifically from its params array, which mirrors data/report_params.csv. Never hardcode a report's fields in app.js; if a field is missing, the catalog CSV is where it belongs.
• Errors follow one contract from the server: {status, code, message, field?, detail?}. A field renders under that specific input; its absence means the message goes to the page-level banner. Keep this as the only error-rendering path — don't add a second one for a new endpoint.