Typed arguments, calculated tables, spans, closed-world fonts, top-level fnt/ and env/

Sync with klammertext-dev through b90b0e09:

- Argument types end to end: :python_cast values are applied (Python
  @eval receives real bools/numbers/lists), argument values are
  validated against their argtype patterns with the argtype's
  description as the error message, argtypes can declare :default
  (overridable per declaration), and parameterized type families are
  supported: rest(N) casts a rest argument to an N-dimensional list
  (bar-count = dimension).
- Unified indexed_range syntax (selector with parenthesized subsets,
  composable mnemonic names) for table lines and spans.
- Table klammer: caption fonts fixed in both targets, :column_width /
  :leading / :colsep wired, :colspan and :rowspan render (HTML
  attributes; \multicolumn / \multirow), calculated cell values (:calc)
  with prefix operators, display-precision semantics, :calc_format and
  :decimal period|comma.
- Fonts: closed-world resolution on the Klammertext font store
  (infrastructure in mac/font_store; no Google Fonts links or fetch).
  Default fonts live in the top-level fnt/; additional fonts install
  into KLAMMERTEXT_FONTS directories via kdesc --font (list, samples,
  preview, install — classification by font metadata).  CSS font family
  names are quoted (digit-initial families were silently lost).
- Environment files moved from mac/env/ to the top-level env/; shell
  profiles source env/runtime.env.  Dead per-host variants removed.
- Container: fnt/ ships in the image; curl removed (no network use).

doc/install/macos_source_install.md

@@ -3,7 +3,7 @@
 Companion to `linux_source_install.md`. Verified on an Apple-Silicon Mac
 (arm64, macOS 26 "Tahoe"). Klammertext's core (engine, SKS, HTML/LaTeX,
 `@image`) builds and runs natively with Apple Clang; the cross-platform build
-environment (`mac/env/makefile.env`) auto-detects the OS via `uname`.
+environment (`env/makefile.env`) auto-detects the OS via `uname`.
 
 ## 1. Toolchain prerequisites
 
@@ -63,7 +63,7 @@ ffmpeg/openexr/etc.)
 ```sh
 git clone https://git.andykopra.com/ack/klammertext.git ~/projects/klammertext
 # Set up the runtime environment (KLAMMERTEXT_HOME, PATH); add to ~/.zprofile:
-echo 'source "$HOME/projects/klammertext/mac/env/runtime.env"' >> ~/.zprofile
+echo 'source "$HOME/projects/klammertext/env/runtime.env"' >> ~/.zprofile
 ```
 
 The single self-configuring `runtime.env` self-locates `KLAMMERTEXT_HOME` from
@@ -132,7 +132,7 @@ variable **and** prepend it to `PATH`, since `runtime.env.local` is sourced
 after the main `PATH` is built:
 
 ```sh
-cat >> "$KLAMMERTEXT_HOME/mac/env/runtime.env.local" <<'EOF'
+cat >> "$KLAMMERTEXT_HOME/env/runtime.env.local" <<'EOF'
 export KLAMMERTEXT_TEXLIVE_BIN=/usr/local/texlive/2025basic/bin/universal-darwin
 export PATH="$KLAMMERTEXT_TEXLIVE_BIN:$PATH"
 EOF