chore: rebrand package metadata, pin engines and drop tooling cache

- package.json: homepage/repository point at this repository, node >=22 declared, @mariozechner/pi-coding-agent added as devDependency (extensions/piagentui-server.ts imports it)
- Cargo.toml: repository field filled
- .pi-lens/ ignored and its cached review graph removed from tracking
- three material icons replaced by their 32x32 sources (the committed 16x16 files were broken)

public/material-icons/assembly.svg

@@ -1 +1 @@
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+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32"><path fill="#ff6e40" d="M8 6V2H4a2 2 0 0 0-2 2v24a2 2 0 0 0 2 2h4v-4H4V6Zm16-4v4h4v20h-4v4h4a2 2 0 0 0 2-2V4a2 2 0 0 0-2-2Zm-4 4h-2a2 2 0 0 0-2 2v4a2 2 0 0 0 2 2h2a2 2 0 0 0 2-2V8a2 2 0 0 0-2-2m-2 6V8h2v4Zm-4 6h-2a2 2 0 0 0-2 2v4a2 2 0 0 0 2 2h2a2 2 0 0 0 2-2v-4a2 2 0 0 0-2-2m-2 6v-4h2v4Zm0-18c0 2 0 2-2 2v2h2v4h2V6Zm8 12c0 2 0 2-2 2v2h2v4h2v-8Z"/></svg>

public/material-icons/folder-database-open.svg

@@ -1 +1 @@
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+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32"><path fill="#ffca28" d="M28.967 12H9.442a2 2 0 0 0-1.898 1.368L4 24V10h24a2 2 0 0 0-2-2H15.124a2 2 0 0 1-1.28-.464l-1.288-1.072A2 2 0 0 0 11.276 6H4a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h22l4.805-11.212A2 2 0 0 0 28.967 12"/><ellipse cx="24" cy="14" fill="#ffecb3" rx="8" ry="4"/><path fill="#ffecb3" d="M24 26c-4.418 0-8-1.79-8-4v4c0 2.21 3.582 4 8 4s8-1.79 8-4v-4c0 2.21-3.582 4-8 4"/><path fill="#ffecb3" d="M24 20c-4.418 0-8-1.79-8-4v4c0 2.21 3.582 4 8 4s8-1.79 8-4v-4c0 2.21-3.582 4-8 4"/></svg>

public/material-icons/folder-database.svg

@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><path fill="#ffca28" d="m6.922 3.768-.644-.536A1 1 0 0 0 5.638 3H2a1 1 0 0 0-1 1v8a1 1 0 0 0 1 1h12a1 1 0 0 0 1-1V5a1 1 0 0 0-1-1H7.562a1 1 0 0 1-.64-.232"/><path fill="#ffecb3" d="M12 5a4 2 0 0 0-4 2 4 2 0 0 0 4 2 4 2 0 0 0 4-2 4 2 0 0 0-4-2M8 8v2c0 1.105 1.791 2 4 2s4-.895 4-2V8c0 1.105-1.791 2-4 2s-4-.895-4-2m0 3v2c0 1.105 1.791 2 4 2s4-.895 4-2v-2c0 1.105-1.791 2-4 2s-4-.895-4-2"/></svg>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32"><path fill="#ffca28" d="m13.844 7.536-1.288-1.072A2 2 0 0 0 11.276 6H4a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h24a2 2 0 0 0 2-2V10a2 2 0 0 0-2-2H15.124a2 2 0 0 1-1.28-.464"/><ellipse cx="24" cy="14" fill="#ffecb3" rx="8" ry="4"/><path fill="#ffecb3" d="M24 26c-4.418 0-8-1.79-8-4v4c0 2.21 3.582 4 8 4s8-1.79 8-4v-4c0 2.21-3.582 4-8 4"/><path fill="#ffecb3" d="M24 20c-4.418 0-8-1.79-8-4v4c0 2.21 3.582 4 8 4s8-1.79 8-4v-4c0 2.21-3.582 4-8 4"/></svg>