# 035 — Collapsible primary UI sections

## Summary

`App.tsx` stacks the Log viewer (`LogTimeline` + `LogPreview`), Params
([034](034-params-declaration-ui.md)), `Metrics`, and `Dashboards` vertically
with no way to collapse any of them. On a small screen — or just when only
one section is being worked on — the others take up space and force
scrolling. Make each section collapsible.

## Scope

- Each of the four sections (Log viewer, Params, Metrics, Dashboards) gets a
  collapse/expand toggle in its header, next to its existing "?" help icon.
- Collapsed state persists across reloads per-section, via `localStorage`
  (same pattern as `LogPreview`'s `VISIBLE_PARAM_COLUMNS_STORAGE_KEY` at
  `webapp/src/components/LogPreview.tsx:13`).
- A collapsed section still shows its header (title + toggle), just not its
  body/content.
- Collapsing a section must not tear down state that would be lost/reset on
  re-expand (e.g. `Dashboards`' in-progress panel edits, `Metrics`' declare
  form) — hide with CSS/conditional render at the container level, not by
  unmounting stateful subtrees.

## Acceptance criteria

- Each section can be independently collapsed and re-expanded.
- Reloading the page preserves each section's collapsed/expanded state.
- Collapsing a section with unsaved in-progress input (e.g. a half-filled
  Metrics declare form) and re-expanding it preserves that input.

## Depends on

- [034 — Params declaration UI](034-params-declaration-ui.md)