feat(plot): improve topic auto-detect, TF support, and chart UX.

[joaner]

Make Plot easier to use for multi-type ROS data by fixing path detection, supporting TFMessage, and adding zoom, reset, and inline legend controls.

Description

This PR upgrades the Plot panel for multi-type ROS data and better in-chart interaction:

• Topic auto-detect & path selection
  • Fix incorrect jointStateFields overriding non-JointState topics (e.g. PoseStamped no longer defaults to position[:])
  • Add generic numeric field discovery (fieldDiscovery.ts) and a topic field tree in settings
  • Merge multiple recommended scalar paths in plotTopicService (comma-separated defaults)
• TFMessage support
  • Register tf2_msgs/TFMessage with a dedicated adapter
  • Resolve transforms[:].transform.translation.x/y/z with stable keys/labels via child_frame_id
  • Keep TF defaults lower priority so they don’t override JointState and similar topics
• Chart interaction
  • Mouse wheel zoom: default X; Shift → Y; Ctrl/Meta → X+Y
  • Drag pan: default X; modifier keys for Y / XY
  • Per-axis manual viewport state with resetViewport API
  • Show “Reset zoom” only when the viewport is manually adjusted; double-click also resets
• Inline chart legend
  • New PlotChartLegend overlay (top-left, collapsed by default)
  • Collapsed: up to 1 entry, semi-transparent until hover/focus
  • Expanded: search, show/hide all, Only, scrollable full list
  • Fixed width (w-80) to avoid layout jump; collapsed view prefers currently visible series after Only
• Tests & i18n
  • Add/update Plot unit tests (topic service, field discovery, legend, viewport, TF paths, etc.)
  • Update en / zh / ja panels.json strings for reset zoom, legend, and topic fields

Motivation / related issue

Plot previously struggled with non-JointState message types, showed blank charts for /tf (TFMessage), and lacked Foxglove-like zoom/pan/reset and an in-chart legend. This change makes common ROS workflows work out of the box and
improves day-to-day chart usability.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing behavior to change)
• Documentation update
• Refactor / internal cleanup (no behavior change)

Checklist

• npm run lint passes with no errors
• npm test passes (unit tests; Plot suite ~140 cases)
• npm run build and npm run build:lib succeed
• New behavior is covered by tests (or explain why tests aren't applicable)
• Documentation updated (README, API.md, EMBEDDING.md) if the public API changed
• Breaking change: all affected call sites updated and migration path described in PR description

API compatibility

N/A — changes are confined to the Plot panel and related i18n strings; no exported public API changes.

Screenshots / recordings

Recommended before merge:

• Plot with PoseStamped / JointState auto-detected paths
• /tf showing per-child_frame_id translation series
• Zoom/pan + “Reset zoom” overlay
• Collapsed vs expanded inline legend, including Only behavior