feat(view): export plotted data (CSV/XLSX) and plot (HTML)

[simontaurus]

Summary

Adds a dashboard-level Export section (compact collapsible card in Plot Controls) to the archive views (DataToolView, ProcessObjectView; LiveDataToolView keeps working) with three FileDownload actions on BaseDataView. Additive and backward compatible.

Download CSV / XLSX

A unit-aware pint-pandas table of every checked channel:

• Numeric channels become pint columns in the selected display unit; text-log channels become plain object columns (so channels from a different display group are included too).
• A tolerant _dequantify writes a two-row (label, unit) header; column keys stay unit-free.
• Rows capped at EXPORT_MAX_ROWS (1,000,000) via uniform downsampling (logged).
• Composite sub-fields get unique labels, with a dedupe safety net so duplicate names cannot collapse a column.

Download plot (HTML)

A standalone interactive Bokeh file:

• Figures are rebuilt fresh and detached (a model may live in only one document) and pinned to a fixed frame size so they render outside a sizing container.
• The log console is embedded below the plots as a width-matched, scrollable Div.

Extensibility

Views supply export_series() (tidy records) and _make_figures/_export_figures hooks; the public figures property still exposes the live figures for host annotation. Export deps (pandas, pint-pandas, openpyxl) are an optional export extra, imported lazily; buttons disable with a hint when absent.

Tests

• Unit tests: DataFrame build + alignment, dequantify, row cap, text column, label dedup.
• Playwright browser tests: download the CSV and HTML and assert the unit header, the text channel, the embedded log console, and a rendered (non-collapsed) plot. They self-skip without Playwright/Chromium (export extra + Chromium are not in CI), so they run locally/manually.
• Full offline suite green; flake8 clean. Local *.sqlite databases are gitignored.

Browser testing surfaced (and this PR fixes) three real bugs: composite-label column collapse, the file_html shared-document error, and the collapsed standalone-HTML plot frame.

Notes

Follow-up (tracked separately): factor the pint/CSV table logic into a generic TabularData base in opensemantic.core and reuse it from both this export and opensemantic.characteristics.quantitative.