Add slides skill icons (#221)

## Summary
- add a dedicated small SVG icon for the curated `slides` skill
- add a 100x100 PNG large icon asset for the skill card
- wire both assets into `skills/.curated/slides/agents/openai.yaml` so
the skill uses the new branding in the UI

## Validation
- `git diff --check`
- verified `skills/.curated/slides/assets/slides-small.svg` is valid SVG
- verified `skills/.curated/slides/assets/slides.png` is a 100x100 PNG

Co-authored-by: Ed Bayes <@openai.com>

skills/.curated/slides/agents/openai.yaml

@@ -1,4 +1,6 @@
 interface:
   display_name: "Slides"
   short_description: "Create and edit PPTX slide decks"
+  icon_small: "./assets/slides-small.svg"
+  icon_large: "./assets/slides.png"
   default_prompt: "Use $slides to create or update this PPTX slide deck with PptxGenJS and validate the layout."

skills/.curated/slides/assets/slides-small.svg

@@ -0,0 +1,3 @@
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M13.4678 7.86641C13.4678 7.29758 13.4671 6.90292 13.442 6.5961C13.4174 6.29551 13.372 6.12642 13.3076 6.00001C13.1669 5.7238 12.9424 5.49935 12.6662 5.3586C12.5398 5.2942 12.3707 5.24879 12.0701 5.22423C11.7633 5.19916 11.3686 5.19845 10.7998 5.19845H5.19981C4.63097 5.19845 4.23631 5.19916 3.92949 5.22423C3.62893 5.24879 3.4598 5.2942 3.3334 5.3586C3.0572 5.49935 2.83273 5.7238 2.69199 6.00001C2.62758 6.12642 2.58218 6.29551 2.55762 6.5961C2.53255 6.90292 2.53184 7.29758 2.53184 7.86641V9.86641C2.53184 10.4352 2.53255 10.8299 2.55762 11.1367C2.58218 11.4373 2.62759 11.6064 2.69199 11.7328C2.83273 12.009 3.05721 12.2335 3.3334 12.3742C3.45981 12.4386 3.62893 12.484 3.92949 12.5086C4.23631 12.5337 4.63097 12.5344 5.19981 12.5344H10.7998C11.3686 12.5344 11.7633 12.5337 12.0701 12.5086C12.3707 12.484 12.5398 12.4386 12.6662 12.3742C12.9424 12.2335 13.1669 12.009 13.3076 11.7328C13.372 11.6064 13.4174 11.4373 13.442 11.1367C13.4671 10.8299 13.4678 10.4352 13.4678 9.86641V7.86641ZM9.81465 2.11563L12.0053 2.13438L12.1123 2.1461C12.3542 2.19814 12.5344 2.41482 12.5318 2.67188C12.5292 2.92875 12.3448 3.14096 12.1021 3.18829L11.9943 3.19845L9.80996 3.1797C7.87499 3.16721 6.50265 3.17347 4.00527 3.19845C3.71153 3.20138 3.4708 2.96561 3.46777 2.67188C3.46484 2.37813 3.7006 2.1374 3.99434 2.13438C6.49686 2.10936 7.87466 2.10313 9.81465 2.11563ZM14.5318 9.86641C14.5318 10.4177 14.5324 10.8633 14.5029 11.2234C14.473 11.5897 14.4095 11.9143 14.2561 12.2156C14.0133 12.6921 13.6255 13.0799 13.149 13.3227C12.8477 13.4761 12.5231 13.5396 12.1568 13.5695C11.7966 13.599 11.3511 13.5984 10.7998 13.5984H5.19981C4.64853 13.5984 4.20297 13.599 3.84277 13.5695C3.47655 13.5396 3.15187 13.4761 2.85059 13.3227C2.37416 13.0799 1.98631 12.6921 1.74356 12.2156C1.5901 11.9143 1.52661 11.5897 1.49668 11.2234C1.46725 10.8633 1.46777 10.4177 1.46777 9.86641V7.86641C1.46777 7.31514 1.46725 6.86958 1.49668 6.50938C1.52661 6.14315 1.59012 5.81849 1.74356 5.5172C1.98631 5.04077 2.37416 4.65292 2.85059 4.41016C3.15188 4.25671 3.47653 4.19322 3.84277 4.16329C4.20297 4.13386 4.64853 4.13438 5.19981 4.13438H10.7998C11.3511 4.13438 11.7966 4.13386 12.1568 4.16329C12.5231 4.19322 12.8477 4.25671 13.149 4.41016C13.6255 4.65292 14.0133 5.04077 14.2561 5.5172C14.4095 5.81849 14.473 6.14315 14.5029 6.50938C14.5324 6.86958 14.5318 7.31514 14.5318 7.86641V9.86641Z" fill="currentColor"/>
+</svg>