Tp-Note v1.27.1

Fixes:
- Percent-encode local links (viewer and --export) so '#', '?', and spaces
  in path segments survive; a directory or file name containing '#' no
  longer 404s in the viewer.
- Strip Nix store RPATH and patch the ELF interpreter so the x86_64 .deb,
  GNU tar.gz, and ARM (aarch64/armv7l) cross-compiled binaries run on
  non-Nix systems.

Dependencies:
- Switch syntect to the pure-Rust fancy-regex backend.
- Update tpnote-lib to 0.46.8 and tpnote-html2md to 0.3.10, including an
  html5ever/markup5ever 0.40 upgrade.
- Routine dependency updates across the workspace.

Tests:
- tests/multi-user: add TPNOTE_TEST_BIN override to test an installed
  binary.

Docs:
- Manual, flake, and README updates.