Tp-Note v1.26.6

A bugfix release centred on the file-annotation templates, plus routine
dependency upgrades.

- Piped front matter now passes through when annotating a file: a YAML
  header supplied on stdin or the clipboard can override title,
  subtitle/keywords, author, date and sort_tag, and any extra fields are
  preserved in the new note's header (default and zettel schemes).
- Fixed a crash ("value must be a string") when annotating files whose
  stem contains no '--' subtitle separator: out-of-bounds nth() returns
  None, which default() now substitutes (boolean=true).
- Removed fragile trunc calls from pipelines whose values are not
  guaranteed to be strings.
- Fixed a whitespace-trim bug in the zettel scheme that glued the
  closing '---' header marker to the last field when no front matter
  was piped, leaving the YAML header unterminated.
- Upgraded compatible dependencies.
- Published crates: tpnote-html2md 0.3.9, tpnote-lib 0.46.5,
  tpnote 1.26.6.

Installers and standalone binaries for Windows, macOS, Linux and
Debian/Ubuntu are attached below.