feat(mcp-server): make Recent Activity rows collapsible by default

[dehuaichendragonplus]

Why

The MCP Server window's Recent Activity panel rendered every row's full
structured result (or embedded screenshot) at all times. On a busy session
with dozens of tool calls this had two costs:

• Performance: each fully-expanded card carries its own parsed JSON tree
  of colored key/value Labels (or a decoded screenshot Image), so a long
  session accumulates dozens of these live UI subtrees at once. Layout and
  repaint of the panel became noticeably sluggish as the list grew.
• Signal-to-noise: with every row always fully expanded, the one entry a
  user actually wanted to check was buried under a wall of detail from
  unrelated calls, making the panel hard to scan.

What changed

• Collapsed by default, click to expand: each row now shows a one-line
  summary by default. Clicking the header row or the summary line expands
  it in place (both are wired up since they are sibling elements, not nested).
• Latest entry auto-expands, but manual state always wins: the most
  recently added row still expands automatically so the newest result is
  visible without an extra click. A small per-row RowExpandState tracks
  whether a user has manually toggled a row; when a new entry becomes the
  latest, the previously auto-expanded row collapses back unless the user
  touched it themselves in the meantime -- manual choices are never
  overridden by the "latest" auto-expand behavior, and any row a user
  expanded (auto-latest or not) stays expanded across future entries.
• Summary width now tracks the panel, in both directions: the one-line
  summary previously used a fixed character cap before appending an ellipsis,
  which either truncated it well short of the available width or couldn't
  grow when the window was widened. It now relies on the default
  stretch-to-parent cross-axis sizing (matching how the header row already
  behaves) with minWidth = 0 so the NoWrap text's intrinsic width can't
  fight a relayout in either direction, and lets CSS TextOverflow.Ellipsis
  clip it at whatever the row's real width is on every relayout.
• Consistent, formatted hover tooltip: hovering a row (header or summary
  line) shows the same formatted, multi-line detail text the expanded view
  renders. A plain card.tooltip assignment isn't enough: an ellipsis-
  truncated Label supplies its own default tooltip (its raw, unformatted
  text) the moment it's hovered, which pre-empts an ancestor's tooltip and
  made the header and the summary line show different content. This
  intercepts the TooltipEvent during the trickle-down (capture) phase on
  the card, before it reaches any child, so the same formatted value always
  wins regardless of which part of the row is hovered.

Validation

• request_recompile / get_compilation_errors: no errors.
• Verified via execute_code reflection against the live VisualElement
  tree of an open MCP Server window (not just visual screenshots):
  • resolvedStyle.display for each row's details container confirms
    collapsed-by-default and toggles correctly on a simulated ClickEvent
    sent to both the header row and the summary line.
  • Resizing the window narrow (450px) then wide (1200px) and re-measuring
    resolvedStyle.width on the summary Label confirms it shrinks and
    grows back to match the card's actual width.
  • Manually expanding an older row, then adding a new entry, confirms the
    previous auto-expanded ("latest") row collapses while the manually
    expanded row and the new latest row both stay/become expanded.
  • Dispatching a real TooltipEvent to the header, an inner header Label,
    and the summary Label of several rows confirms all three now resolve
    to the exact same formatted tooltip text.

CHANGELOG.md updated under [Unreleased].