# 112 — Let a single dashboard panel pop out into its own window

## Summary

There's already a pop-out mechanism for whole primary sections (log,
params, metrics, dashboards) — `PopOutButton` opens a new tab at
`?section=<id>` and `App.tsx` reads that query param at startup to
render a standalone, full-page version of just that section (see
`webapp/src/components/CollapsibleSection.tsx:193-232` and
`webapp/src/App.tsx:129-140`, `:372-376`). That grain is a whole
section, not a single panel — the Dashboards section can only be
popped out in its entirety (all panels of the active dashboard, or
all dashboards stacked via `AllDashboardsView`,
`Dashboards.tsx:107-135`). This ticket adds the finer-grained version:
popping out one panel from one dashboard into its own window,
independent of the rest of that dashboard.

## Where

- `webapp/src/components/Dashboards.tsx:46-92` (`PanelPreview`) is
  the component that would need to render standalone, full-page, the
  same way `StandaloneLog`/`StandaloneParams`/`StandaloneRanged` do
  today for whole sections (referenced in `App.tsx:373-376`, exact
  component locations elsewhere in `Dashboards.tsx`/`Metrics.tsx` per
  the skeleton read during this ticket's writeup — re-read
  `Dashboards.tsx` in full before implementing, since it was read via
  repowise's skeleton view here and several ranges (`:1-45`, `:136-
  434`) were elided).
- `webapp/src/components/CollapsibleSection.tsx:193-206`
  (`PopOutSectionId`, `popOutUrl`) — the existing section-grain
  pop-out routing. A panel-grain pop-out needs to identify a specific
  `(dashboardId, panelId)` pair in the URL, not just a section name —
  either extend this query-param scheme with `dashboardId`/`panelId`
  params alongside `section=dashboards`, or give panels their own
  distinct query shape if reusing `PopOutSectionId` doesn't fit
  cleanly.
- `webapp/src/App.tsx:129-140` (`parsePopOutQuery`), `:372-376` (the
  dispatch on parsed `section`) — where the new panel-grain case needs
  a branch, reading whatever new params are added above.
- Each `Panel` (`webapp/src/lib/api.ts`'s `Panel` type, imported at
  `Dashboards.tsx:19`) needs a stable identifier already, or one to
  add, so a popped-out URL can point back at "this exact panel of
  this exact dashboard" — check whether `Panel` already carries an
  `id` field before inventing a new addressing scheme.

## Direction

- Mirror the existing section pop-out exactly: a small pop-out button
  per panel (using or extending `PopOutButton`,
  `CollapsibleSection.tsx:209-232`) that opens `?section=dashboards&
  dashboardId=<id>&panelId=<id>`, plus range params the same way
  `popOutUrl` already carries over a rolling preset or fixed range
  (`CollapsibleSection.tsx:196-206`).
- The standalone page for this case renders just that one panel's
  `PanelPreview` (or a thin wrapper around it) full-page — no
  dashboard chrome, no other panels — analogous to how
  `StandaloneRanged` (`App.tsx:179-...`) drives `LogTimeline`'s
  picker UI on its own poll cadence for the metrics/dashboards
  standalone views.
- The popped-out panel window should keep polling independently
  (same `POLL_MS` pattern `PanelPreview` already uses,
  `Dashboards.tsx:52-55`) rather than freezing at open time.

## Scope

- One panel popping into a new browser tab/window, matching the
  existing section pop-out's mechanism (new tab via `window.open`,
  not an in-app floating/detached window widget) — stay consistent
  with the pattern already established for log/params/metrics/
  dashboards rather than introducing a second, different pop-out
  mechanism.
- Out of scope: editing a panel's query/chart type from the popped-out
  view — read-only preview only, matching what pop-out gives you for
  the other sections today.
- Out of scope: [[110-legend-click-to-focus-series]] and
  [[111-scrollable-panel-legend]] — this ticket is purely about the
  window/routing mechanism; the popped-out panel should get those
  legend behaviors for free once they land in `PanelChart`, since
  it's the same component, but implementing them isn't this ticket's
  job.