feat(odf): read the enhanced geometry languages, formulas and path alike

`draw:enhanced-geometry` is what makes a custom shape an arrow, a callout or a
star, and it says so in two small languages: `draw:formula` (20.36) and
`draw:enhanced-path` (19.145). Neither was read, so all 350 of them in the test
corpus rendered as rectangles.

`odf_enhanced_geometry.cpp` implements both as pure functions over strings —
nothing is wired into the element model yet, that is the next change:

- `evaluate_formula` is recursive descent over 20.36: `$N` modifiers, `?name`
  equation references resolved through a caller-supplied lookup, the named
  view-box values, and `abs sqrt sin cos tan atan min max atan2 if`. The
  trigonometric functions take radians; the corpus settles it by writing
  `sin(105*(pi/180))`.
- `convert_enhanced_path` turns every command of 19.145 into an svg `d`.

Two things worth knowing about the path conversion. An arc is emitted in
segments of at most a half turn, which means the large-arc flag is never needed
and `U 10800 10800 10800 10800 0 360` — a full turn, which a single svg `A`
cannot express, and 116 of the corpus's commands — still draws. And `F` and `S`
are read and dropped: painting one subpath with a different fill or stroke is
more than one `d` can say.

Tested from string literals; the geometry needs no fixture to exercise.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017XABfEapaADjFQCt1vjmDF

Author: andiwand

CMakeLists.txt

@@ -180,6 +180,7 @@ set(ODR_SOURCE_FILES
         "src/odr/internal/odf/odf_crypto.cpp"
         "src/odr/internal/odf/odf_document.cpp"
         "src/odr/internal/odf/odf_element_registry.cpp"
+        "src/odr/internal/odf/odf_enhanced_geometry.cpp"
         "src/odr/internal/odf/odf_file.cpp"
         "src/odr/internal/odf/odf_flat_file.cpp"
         "src/odr/internal/odf/odf_geometry.cpp"

src/odr/internal/odf/PLAN.md

@@ -120,13 +120,18 @@ label comes out empty.
 `vector-effect="non-scaling-stroke"` on the path: the view box scales, and with
 `preserveAspectRatio="none"` unevenly, which the stroke must not follow.
 
-### 3 — `draw:enhanced-path` and `draw:equation`, parser only
-
-The formula mini-language (`$N` modifiers, `?fN` references, the eleven
-functions the corpus uses plus the rest of 20.36) and the path grammar
-(`M L C Z N U X Y` plus the commands 19.145 defines and the corpus does not
-use). Pure functions over strings, unit-tested from string literals, no
-rendering and no element-model change. The largest single piece.
+### 3 — `draw:enhanced-path` and `draw:equation`, parser only — landed
+
+`odf_enhanced_geometry.cpp`: the formula language of 20.36 (`$N` modifiers,
+`?name` references, the named view-box values, `abs sqrt sin cos tan atan min
+max atan2 if`) and every command of 19.145, converted to an svg `d`. Pure
+functions over strings, unit-tested from string literals.
+
+Decisions worth knowing: `sin`/`cos` take radians, which the corpus confirms by
+writing `sin(105*(pi/180))`; an arc is emitted in segments of at most a half
+turn, so the large-arc flag is never needed and a full `U … 0 360` — which one
+svg `A` cannot express — still draws; `F` and `S` are read and dropped, since
+painting one subpath differently is more than one `d` can say.
 
 ### 4 — enhanced geometry, rendered