Release 0.9.10  "Best" - Ranges and documentation

This release is primarily a refinement of ranges and a documentation update.

New features
============

* Always display infinity ranges with range notation
* Add constant for `-∞`
* Add support for ranges in `Explode` / `Obj→`
* Add support for delta and percent ranges in `ToDecimal`
* Allow `Copy` to target a local variable or setting
* Support `True` and `False` in  `→Num`

Bug fixes
=========

* Replace `log` with `ln`, make `log` be base-10 logarithm
* Check zero-divide in ranges
* Fix the implementation of trig functions for ranges
* Fix incorrect command associated to the `%T` alias (should be `%Total`)
* Adjust help for `log10` and `ln`
* Avoid pushing a null pointer on the stack on error evaluating constants
* Add missing `Ⓒ` sign in uncertainty for `Epl`
* Fix constant evaluation referencing `this` after it may have moved
* Report missing current directory in `Purge`
* Report errors when purging invalid objects in `Purge` and `PurgeAll`
* Avoid `ClearThingsMenu` in tests, the key maps to forward delete in editor

Improvements
============

* keyboard: Update layout to include `σ` character
* Remove the `state/Test.48S` file, it's not longer relevant
* Add `constant` case to `object::is_negative`
* Add `DATE-` as an alias for `DDAYS`
* Add `PgAll` as an alias for `PurgeAll`
* More systematic purging of environment and variables between tests
* Add check in test suite that we actually purged special variables
* Refresh authors list
* Move documentation for `PPAR` to `plot.md`
* Avoid date conversions during constant evaluation
* Accelerate and improve the display of constant values in menus
* Add `launch.json` and `tasks.json` build configuration generated by Cursor
* Send a `START_TEST` command at start of test, refresh simulated battery
* Cursor-assisted review of missing command documentation
* Cursor-assisted generation of content in the Quickstart guide
* Cursor-assisted improvements to grammar and spelling
* Documentation and examples for `Blank` variants
* Documentation and examples for `Gray` and `RGB`
* Documentation and examples for `PMIN`, `PMAX`, `XRNG`, `YRNG`
* Documentation and examples for `Eq` and equations
* Add examples for list sum, product and difference commands

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>