0.41.0 — Interactive Slice tool

Added

• Interactive Slice tool for pcolormesh/imshow (options=["slice"]).
  Scrub any row or column of a mesh as a 1-D profile with a play/step
  slider, toggle between the heatmap (with a dashed cursor) and the profile,
  fix the value axis to auto / colorbar / custom bounds, and couple every
  mesh sharing the same grid to one global slider with "Link all matching
  axes" -- built for figures with hundreds of meshes, where per-axes link
  checkboxes are not workable. Off until "Enable Slice" is checked; curvilinear
  meshes are excluded (no single row/column to slice).

• Modular toolbar via options=. to_html/save/show/
  show_in_jupyter/Report.save (and PlotPressWidget) take
  options=[...] for tools beyond the core toolbar (Pan/Zoom, Home, Fit
  Width, Axes, Point Picking, Annotate, File), which every page keeps.
  Nothing existing changes unless asked for.

• Slice companion panel. The Slice menu's profile can be drawn in a
  strip carved out of the mesh's own axes (above it for an X slice, to its
  left for a Y slice), beside the heatmap and aligned through every pan/zoom,
  instead of replacing it. A radio in the menu switches between that
  (the default), the profile replacing the heatmap, and a cursor-only heatmap.
  Point Picking works on the strip -- a click pins the nearest profile sample
  (x, y, value), which follows the slider and pan/zoom, steps with the
  arrow keys (staying on the strip's edge, value in red, if it goes off the
  range) -- and Snap pins to
  slice (a checkbox in the menu's own "Slice view" group) links pins in both
  directions: a heatmap pin gets a mirror on the shown profile, and a pin placed
  on the profile gets one on the heatmap cell it points at. Extract ignores profile
  pins and reports the heatmap cell instead (never the same cell twice). When profile pins are left out
  (Snap off), the Extract panel warns and points to Snap pins to slice. The original stays
  put and each pair shares a label color.
  A colorbar attached to a sliced mesh shrinks to the heatmap's share of its axes
  when the strip is above it, so the two stay aligned.

• A colorbar shared by several axes shrinks with their heatmaps when every one of
  them gets a strip (it stays as drawn if only some do).

• Save / Save As keep the Slice state. A saved page reopens with Slice enabled,
  in the same view and orientation, on the same chosen axes, with the same link/snap
  settings, value range and slider position, and with its profile pins.

• Point Picking works on the "Profile replaces heatmap" view too. A click picks a
  profile sample instead of a hidden heatmap cell, and pins carry across a switch
  between the two profile views.

• The companion strip now works on more axes. Axes with fixed ticks
  (set_xticks/set_yticks), axis("off"), and axes with a twinx/twiny
  or secondary axes (which shrink together with their parent) get a strip too;
  their static ticks are remapped to the smaller heatmap. An inset axes is left
  out of Slice altogether, and the axes it sits on still gets just the cursor and
  slider. Also
  fixes a twin's ticks being redrawn on the wrong edge (and its parent's axis
  doubled) when the view changed.

• Choose which axes to slice. The Slice menu has an "Axes to slice" radio --
  All axes or Selected axes -- where selecting axes is done by clicking them on the
  figure; only the chosen axes get a slider, cursor and strip,
  and "Link all matching axes" couples just those. The axes startup setting takes
  the axes (or indices) to start with.

• Startup settings for a tool. Pass options as a dict to start a tool in
  a chosen state -- e.g. options={"slice": {"enabled": True, "view": "companion", "orientation": "y", "link_all": True, "range": "colorbar"}} --
  rather than switched off; values are validated up front.

• Gridlines on the Slice profile. A "Gridlines on profile" checkbox (and a
  grid startup setting, default on) draws light lines on the strip and on the
  profile-replaces-heatmap view at both the value ticks and the heatmap's own ticks.

• Docs: Slice examples. Four examples in the gridded-data gallery (a heatmap
  row, columns with the replace view, linked meshes, chosen axes) and one at scale
  (a thousand meshes). Every live pcolormesh/image figure in the plot-type
  reference and real-application galleries now opens with Slice enabled, and an
  example can set its own state with _gallery_interactive_options.

Performance

• Slice on a figure with ~1000 pcolormeshes. Enabling Slice went from ~14 s
  (without "Link all") to under a second, a linked slider step from ~3 s to under
  0.1 s, and view/orientation switches from 7-9 s to under 0.5 s. Choosing a subset
  of axes stays at tens of milliseconds per step. The cost was layout thrashing
  (measuring while writing) and per-axes scans of the whole document.

Changed

• The Extract panel now shows JSON by default, with CSV/JSON radios to switch
  the text, and its "Copy CSV" button is now "Copy" (it copies whichever format is
  showing). The two download buttons are unchanged.
• New logo, docs sidebar image and favicon. Refreshed artwork for the three
  images already wired in (assets/plotpress-logo.png, docs/_static/logo.png,
  docs/_static/favicon.png); nothing that references them changed.

Fixed

• Slice: a strip could take more than its own axes. The strip's 28px
  legibility floor ignored how tall the axes actually was, so on a stack of short
  panels (14 rows in a 5in figure is ~23px each) it claimed more than the whole
  rect and left the heatmap with a negative one -- which draws nothing at all,
  silently, since a negative width/height raises no error. The floor now gives way
  on an axes too small to hold both.
• Slice: an all-NaN row showed the previous row's profile. Under "Profile
  replaces heatmap", stepping onto a row with no values left the last row's line on
  screen: the slider read row 4 while the profile plotted row 3. A pin on such a
  slice likewise stayed visible, still reporting the value it last read.
• Slice no longer fights the legend. Slice and the legend's click-to-hide
  toggle both wrote a mesh's own style.display, so a slider step brought back a
  mesh the reader had just hidden. Each now has its own channel, and a mesh stays
  hidden while either wants it hidden.
• Tick labels stayed put through a zoom. Three long-standing divergences
  between the labels Python renders and the ones the interactive view recomputes:
  an axis with a fractional set_xlocator base relabelled 0/2.5/5/7.5/10 as
  0/3/5/8/10 after the first pan; a lone tick at 0 rendered 0e0; and a tick at
  exactly +-0.5 read 0/-0 as drawn but 1/-1 once zoomed, because
  JavaScript rounds a halfway value away from zero where Python rounds half to
  even. A new 2,707-case parity sweep (tests/test_tick_parity_node.py) covers
  the whole range x locator x format x date x categorical x log grid.
• Tick positions land on their exact step multiples. nice_ticks and
  multiple_ticks accumulated their step by repeated addition, so a tick that
  should be 5.5 came out at 5.499999999999998 and one that should be 0 at
  -3.4e-13 -- the latter printed as a literal -3.4e-13 axis label in the static
  SVG.