feat(visual): refine OFDM ChanEst layout and simplify I/Q scatter presentation

- reorganize per-channel layout with centered I/Q scatter, side-by-side magnitude/group-delay graphs, and echo analysis below
- move DOCSIS channel measurement stats into each channel section and place them above magnitude signal stats
- relabel signal stats to indicate they describe magnitude response data
- remove scatter reference grid, crosshair overlays, and sample-ready status pill
- standardize centered titles and whole-number MHz labels; label magnitude charts/axes in dB
- remove broken all-channel overlay summary graphs to keep ChanEst output reliable
- add temporary measurement_stats filename-based channel mapping fallback for mismatched channel IDs
- regenerate visual docs/previews for GetCapture-ChanEst - 2026-02-22 23:34:38

Author: mgarcia01752

CODING_AGENTS.md

@@ -46,6 +46,9 @@
 - Format capture timestamps as a human-readable date/time string (not raw epoch seconds).
 - Keep channel metadata in a separate block below `Device Info` (for example `Channel`, center/subcarrier frequency).
 - Display frequencies in `MHz` for UI-facing labels; raw `Hz` may be shown secondarily in parentheses when useful.
+- Default UI frequency labels/ticks to whole-number `MHz` (no decimal floats) unless precision is required for the specific visual.
+- Include units in graph titles/axis labels for measured values (for example `Magnitude (dB)` instead of `Magnitude`).
+- Center graph/panel titles for scanability and consistent visual layout.
 - Avoid redundant repetition of values already shown in `Device Info` (for example, do not repeat `MacAddress` in the channel header if it is already in the device table).
 - If `system_description` is missing/partial, render `N/A` for missing fields instead of vendor-specific fallback values.
 - JSON responses may contain multiple upstream/downstream channels; each channel must render as its own graph for the selected graph type.