fix(engine): render card suit glyphs as SVG paths instead of text

The user's first post-migration screenshot showed near-invisible
suit glyphs on every card — the rank rendered at correct size but
the ♠ ♥ ♦ ♣ marks were tiny dots regardless of the requested
20px / 64px font-size.

Root cause: the bundled FiraMono in svg_loader::shared_fontdb
doesn't carry usable Unicode suit glyphs (U+2660-2666). usvg
silently fell back to a substitute rendering at default size,
producing the "tofu" effect.

Fixes by replacing the `<text>` glyph rendering with inline SVG
paths. `suit_path_d(suit)` returns a single closed-perimeter path
authored in a 32 × 32 logical box, then face_svg wraps it in two
`<g transform>` blocks (top-left small + bottom-right rotated
large). Path-based rendering bypasses the font system entirely
— same bytes on every machine, no fontdb dependency, no
substitution risk.

Same path data renders correctly whether filled (♥ ♠) or
outlined (♦ ♣ — the always-on color-blind glyph differentiation
from the design system).

Knock-on changes that must land in this commit per the migration
plan's lockstep rule:

- `EXPECTED` in tests/card_face_svg_pin.rs rebaselined: 52 face
  hashes change (text → path), 5 back hashes unchanged
  (back_svg untouched). The bootstrap pattern in the test
  handled the rebaseline cleanly — empty EXPECTED, re-run,
  paste, re-run.
- assets/cards/faces/*.png regenerated (the 52 face PNGs).
- solitaire_engine/assets/themes/default/*_*.svg regenerated
  (the 52 theme face SVGs that production rasterises at
  startup). Both rendering paths must agree.

Workspace clippy + cargo test --workspace clean. Pin test
passes against the new hashes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

solitaire_engine/assets/themes/default/spades_king.svg

@@ -2,15 +2,24 @@
   <rect x="1" y="1" width="254" height="382" rx="16" ry="16"
         fill="#1a1a1a" stroke="#d0d0d0" stroke-width="2"/>
 
-  <!-- Top-left rank + small suit glyph. -->
+  <!-- Top-left rank in JetBrains-Mono-styled FiraMono (rank digits
+       and letters render correctly in FiraMono; only the suit glyphs
+       needed to escape to paths). -->
   <text x="14" y="44" font-family="Fira Mono" font-size="36" font-weight="700"
         fill="#d0d0d0">K</text>
-  <text x="14" y="68" font-family="Fira Mono" font-size="20"
-        fill="#d0d0d0">&#x2660;</text>
 
-  <!-- Bottom-right large suit glyph, rotated 180° about its own
-       baseline anchor so the glyph reads upside-down. -->
-  <text x="242" y="350" font-family="Fira Mono" font-size="64"
-        text-anchor="end" fill="#d0d0d0"
-        transform="rotate(180 242 332)">&#x2660;</text>
+  <!-- Top-left small suit glyph at (14, 50), 20 × 20.
+       `suit_path_d` is authored in a 32-unit box, so scale 0.625
+       lands the visible glyph at 20 px. -->
+  <g transform="translate(14 50) scale(0.625)">
+    <path d="M16,4 C 9,9 2,14 2,21 C 2,25 5,28 9,28 C 13,28 14,26 14,24 L 13,30 L 19,30 L 18,24 C 18,26 19,28 23,28 C 27,28 30,25 30,21 C 30,14 23,9 16,4 Z" fill="#d0d0d0"/>
+  </g>
+
+  <!-- Bottom-right large suit glyph, 64 × 64, rotated 180° so it
+       reads upside-down (the convention for inverted-corner
+       indicators). The transform pipeline lands the glyph's visible
+       bottom-right at (242, 350) and visible top-left at (178, 286). -->
+  <g transform="translate(242 350) rotate(180) scale(2)">
+    <path d="M16,4 C 9,9 2,14 2,21 C 2,25 5,28 9,28 C 13,28 14,26 14,24 L 13,30 L 19,30 L 18,24 C 18,26 19,28 23,28 C 27,28 30,25 30,21 C 30,14 23,9 16,4 Z" fill="#d0d0d0"/>
+  </g>
 </svg>