Tachyon v1.4.0

Added

• A sticky_folder setting chooses where sticky notes are saved (a plain path; empty, the
  default, keeps <Documents>/tachyon/notes). It applies to notes saved from then on: nothing is
  moved, an existing note keeps its file, and "Reopen sticky note" lists the folder that is set.
  A folder that cannot be written keeps the text in the note and says so. The new command
  palette row "Open sticky notes folder" opens the folder in use, so a changed path never hides
  your notes. A # inside a quoted setting value (a folder named C#) is no longer taken for a
  comment (#109).
• Sticky notes can be plain text: a MD/TXT button in the note header (next to the pin) switches
  the note between Markdown and plain text, the same switch as Ctrl+Shift+M. Each note
  remembers its mode across restarts; its file stays .md (#115).
• A sticky_default_mode setting ("markdown" or "plain", default "markdown") chooses the
  mode a new sticky note starts in. It is in Preferences too (#116).
• Save As follows the new extension: an untitled Markdown document saved as server.log or
  data.json becomes plain text (no Markdown parsing, # stays literal), and a plain-text
  document saved as notes.md becomes Markdown (up to 128 KiB, and never for binary or
  garbled text, so it cannot stall a frame; Ctrl+Shift+M still switches larger ones). The text,
  caret and undo history are kept. Save As suggests untitled.txt for a plain-text document. A
  plain Save keeps a mode you chose with Ctrl+Shift+M (#123).
• "Open with Tachyon" is offered for more text files: .json, .jsonc, .toml, .yaml,
  .yml, .ini, .cfg, .conf, .csv, .tsv, .xml, .env, .gitignore and
  .editorconfig on Windows (next to .txt, .text, .log), and the matching MIME types in
  the Linux desktop entry. They open in plain-text mode (#123).
• Clicking a task-list checkbox toggles it ([ ] / [x]) in the source, as its own undo step,
  without moving the caret, starting a selection, or turning the block into raw Markdown. Works
  in every window, in nested lists, numbered lists and quotes; sticky notes autosave the change
  (#129).
• Mermaid diagrams: a fenced code block marked mermaid shows as a diagram when the caret is
  elsewhere (click it to edit the source). Rendered in the background by a bundled renderer, so
  typing never waits and documents without diagrams cost nothing. A diagram that does not parse
  stays code, with the reason underneath. The mermaid setting turns this off.
• Preferences (Ctrl+,): every setting in one list with its current value and what it does, even
  when the settings file is empty or from an older version. Pick a row to flip it, step to its
  next value, or type a new one (a value Tachyon does not accept says why and changes nothing).
  Changes apply to every window at once and keep the file's comments. "Open settings file" in the
  command palette still opens the file.
• Reset all settings to defaults, from Preferences or the command palette: asks first, then
  rewrites the settings file with every setting and its comment, keeping the old file as
  settings.toml.bak.
• Website: the orbit ring around the hero screenshot is animated, with four small nods to the
  physics of tachyons (escape velocity, arriving before leaving, a reversed jump and a Cherenkov
  lap). A picker under the screenshot chooses one (on phones: tap the screenshot) and the site
  remembers the choice; otherwise one plays at random. Under reduced motion the ring stays
  still. The ring now also shows on phones.
• Website: a new page, "What is a tachyon?", explains the particle behind the name at four reading
  levels (ELI5, ELI13, Standard, ELI-PhD), with interactive diagrams of energy against speed,
  spacetime and simultaneity, the tachyonic antitelephone (3D, drag to turn) and Cherenkov
  radiation, plus cited references. It works without JavaScript and under reduced motion; the 3D
  library loads only when that diagram scrolls into view.

Changed

• Unsaved documents are marked with * in the window title (*notes.md - Tachyon), the
  Windows convention, instead of a bullet (#112).
• Ctrl+, opens Preferences instead of the settings file.