fix(adapters): keep log axis viewports in data units

[jvdd]

Closes #74. Does step 1 of #98.

Change

• Plotly holds a log axis range in log10 units. Client state (state.viewport, client_state.axis_lock_ranges) now always holds data units, as the server and the selections expect.
• Two helpers in plotly/render.js, plotlyRangeToData and plotlyRangeFromData, convert where Plotly ranges meet client state:
  • read: the relayout handler, the axis lock capture, and the selection band fill (second commit);
  • write: syncLayoutViewport and fvApplyAxisLocks.
• The declared axis type decides (isLogAxis): the axis type, else the type in the layout template, as in Plotly. The first render writes the layout before Plotly draws the div, so both directions use the same source.
• The exponent is clamped to the float range, so a far zoom-out never sends Infinity (JSON null, HTTP 422) or 0.
• link_axes still rejects log axes. The message now says that log axes are not linkable yet, and the comment gives the reasons: a linear member of a group can zoom to a range at or below 0, and a group of log axes only is not designed yet.
• Architecture.md describes the units and the conversion.

Impact

• A zoom or pan on a log axis now re-aggregates the visible range. Before, line, histogram and histogram2d traces aggregated with log10 values as data bounds, so the zoomed figure showed the wrong data. This also holds for a log axis declared through update_layout(template=...).
• A lock on a log axis stores and restores data units.
• Second commit: a one-axis selection band on a figure with a log axis (for example an x brush on a histogram with a log count axis) now spans the whole axis. Before, it was placed in log10 units and fell outside the plot.
• A share URL made before this fix with a zoomed log axis stored log10 values. They now read as data units. Those URLs already aggregated the wrong range.

Not in this PR

• Pre-existing bugs on the same boundary: the live preview of a selection-edit drag (_fvOutlineDataRange uses p2r) and linked hover guides (l2p) are still in log10 units on a log axis (fix(adapters): draw linked hover and the edit-drag preview in data units on a log axis #118).
• A viewport bound at or below 0 on a log axis, from flexvizApply or a hand-edited spec: A viewport at or below 0 on a log axis: the client shows another range than the server aggregates #121.

Tests

• New TestLogAxisBrowser: a real mouse drag zoom (with the log type on the axis and in the layout template), a saved viewport on open, a far zoom-out, an axis lock with double-click and reset, and a selection band on a log count axis. Each fails on main, except the far zoom-out: main sends the log10 bounds, which are finite, so that test guards the clamp of this PR. The template case also fails without its commit.
• On this branch merged with main: pytest tests: 2289 passed, 1 skipped. pytest -m browser tests: 323 passed, 12 skipped.

[codspeed]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing fix/log-axis-viewport (c422efd) with main (ea7939b)}