Iterate on Assistant 2 composer UI (#11306)

- Change project index tool rendering in composer
- Update composer UI style

Release Notes:

- N/A

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Co-authored-by: Marshall Bowers <1486634+maxdeviant@users.noreply.github.com>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

assets/icons/code.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-code-xml"><path d="m18 16 4-4-4-4"/><path d="m6 8-4 4 4 4"/><path d="m14.5 4-5 16"/></svg>

assets/icons/spinner.svg

@@ -0,0 +1,13 @@
+<svg width="8" height="8" viewBox="0 0 8 8" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g clip-path="url(#clip0_1803_28)">
+<path d="M0.5 2C0.5 1.17157 1.17157 0.5 2 0.5V0.5C2.82843 0.5 3.5 1.17157 3.5 2V2C3.5 2.82843 2.82843 3.5 2 3.5V3.5C1.17157 3.5 0.5 2.82843 0.5 2V2Z" fill="black" fill-opacity="0.3"/>
+<path d="M7.5 6C7.5 6.82843 6.82843 7.5 6 7.5V7.5C5.17157 7.5 4.5 6.82843 4.5 6V6C4.5 5.17157 5.17157 4.5 6 4.5V4.5C6.82843 4.5 7.5 5.17157 7.5 6V6Z" fill="black" fill-opacity="0.6"/>
+<path d="M2 7.5C1.17157 7.5 0.5 6.82843 0.5 6V6C0.5 5.17157 1.17157 4.5 2 4.5V4.5C2.82843 4.5 3.5 5.17157 3.5 6V6C3.5 6.82843 2.82843 7.5 2 7.5V7.5Z" fill="black" fill-opacity="0.8"/>
+<path d="M6 0.5C6.82843 0.5 7.5 1.17157 7.5 2V2C7.5 2.82843 6.82843 3.5 6 3.5V3.5C5.17157 3.5 4.5 2.82843 4.5 2V2C4.5 1.17157 5.17157 0.5 6 0.5V0.5Z" fill="black"/>
+</g>
+<defs>
+<clipPath id="clip0_1803_28">
+<rect width="8" height="8" fill="white"/>
+</clipPath>
+</defs>
+</svg>