Fork Notesium source and restructure into Go package layout

Initial fork of github.com/alonswartz/notesium into librenotes:
- Source moved to internal/notesium/ (package notesium)
- Thin entry point at cmd/librenotes/main.go
- Module renamed to git.librete.ch/public/librenotes
- main() exposed as notesium.Run()
- LICENSE preserved (MIT), NOTICE added with attribution
- Web assets and completion.bash co-located with embedding code
  to satisfy go:embed path constraints

Closes #3, #34, #35.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/notesium/web/app/index.html

@@ -0,0 +1,124 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <title>Notesium Web</title>
+    <script src="vendor.js"></script>
+    <link rel="stylesheet" href="vendor.css" />
+    <link rel="stylesheet" href="tailwind.css" />
+    <link rel="shortcut icon" href="favicon.svg">
+    <style>
+      ::-webkit-scrollbar { width: 5px; }
+      ::-webkit-scrollbar-track { margin: 6px 0px 6px 0px; }
+      ::-webkit-scrollbar-thumb { background-color: #e5e7eb; border-radius: 5px; }
+      ::-webkit-scrollbar:horizontal { height: 10px; }
+      .dark-scroll::-webkit-scrollbar-thumb { background-color: #64748b !important; }
+
+      .forcegraph .node { fill: #ff7f0e; }
+      .forcegraph .node-label { fill: #1f77b4; }
+      .forcegraph .link { stroke-width: 0.5; }
+      .forcegraph .title { fill: #475569; font-size: 4px; cursor: pointer; alignment-baseline: middle; }
+      .forcegraph .title:hover { text-decoration: underline; }
+
+      .cm-s-notesium-light.CodeMirror { color: #1f2937; background: transparent; min-height: 100%; }
+      .cm-s-notesium-light pre.CodeMirror-placeholder { color: #999; }
+      .cm-s-notesium-light span.cm-comment { color: #8f5536; }
+      .cm-s-notesium-light span.cm-quote { color: #64748b; }
+      .cm-s-notesium-light span.cm-formatting-quote { color: #64748b; }
+      .cm-s-notesium-light span.cm-formatting-list-ul { color: #94a3b8; }
+      .cm-s-notesium-light span.cm-url,
+      .cm-s-notesium-light span.cm-link { color: #4338ca; text-decoration: none; }
+
+      .cm-links-hover span.cm-url:hover,
+      .cm-links-hover span.cm-link:hover { cursor: pointer; text-decoration: underline; }
+      .cm-fat-cursor .CodeMirror-cursor { background: #cbd5e1; max-width: 8px; }
+
+      .cm-conceal .CodeMirror span.cm-url,
+      .cm-conceal .CodeMirror span.cm-formatting-em,
+      .cm-conceal .CodeMirror span.cm-formatting-link,
+      .cm-conceal .CodeMirror span.cm-formatting-code,
+      .cm-conceal .CodeMirror span.cm-formatting-strong,
+      .cm-conceal .CodeMirror span.cm-formatting-strikethrough { font-size: 0px; transition: font-size 0.1s ease-in-out; }
+      .cm-unconceal .CodeMirror-activeline span,
+      .cm-unconceal .CodeMirror-selectedline span { font-size: inherit !important; }
+
+      span.cm-hr { color: #94a3b8; }
+      .cm-conceal span.cm-hr { color: transparent; background: #d1d5db; display: inline-block; width: 100%; line-height: 1px; }
+      .cm-unconceal .CodeMirror-activeline span.cm-hr,
+      .cm-unconceal .CodeMirror-selectedline span.cm-hr { color: #94a3b8; background: initial; display: initial; width: initial; line-height: initial;}
+
+      .CodeMirror-dialog {
+          position: absolute;
+          left: 0;
+          right: 0;
+          bottom: 0;
+          background: inherit;
+          z-index: 15;
+          overflow: hidden;
+          color: inherit;
+          padding: 8px;
+          margin-bottom: 4px;
+          border: 1px #d1d5db solid;
+          border-radius: 8px;
+          backdrop-filter: blur(8px);
+          display: flex;
+          justify-content: space-between;
+      }
+      .CodeMirror-dialog input {
+          border: none;
+          outline: 0;
+          background: 0 0;
+          width: 40em;
+          color: inherit;
+          font-family: monospace;
+          caret-color: black;
+      }
+
+      .cm-s-notesium-light .CodeMirror-gutters { background-color: transparent; border-right: 0px; }
+      .cm-s-notesium-light .CodeMirror-guttermarker-subtle { color: #d1d5db; cursor: pointer; }
+      .cm-s-notesium-light .CodeMirror-guttermarker-subtle:hover { color: black; }
+      .CodeMirror-foldgutter { width: 1.5em; }
+      .CodeMirror-foldgutter-open:after,
+      .CodeMirror-foldgutter-folded:after {
+        content: "\203A";
+        display: inline-block;
+        font-size: 24px;
+        line-height: 1;
+        margin-top: -3px;
+      }
+      .CodeMirror-foldgutter-open:after {
+        margin-left: 1px;
+        transform: rotate(90deg);
+      }
+      .cm-foldmarker {
+        cursor: pointer;
+        display: inline-block;
+        width: 98%;
+        background-color: #e4e4e790;
+        margin-bottom: 1px;
+      }
+      .cm-foldmarker:hover {
+        background-color: #e4e4e7;
+      }
+      .cm-foldmarker-header {
+        font-weight: bold;
+      }
+      .cm-foldmarker-lines {
+        padding-left: 10px;
+        opacity: 50%;
+      }
+    </style>
+  </head>
+  <body tabindex="-1">
+    <div id="app"></div>
+    <script type="module">
+      const { createApp } = Vue
+      import App from './app.js'
+      import { notesiumState } from './state.js'
+      const app = createApp(App)
+      app.config.globalProperties.$notesiumState = notesiumState;
+      app.mount('#app');
+    </script>
+  </body>
+</html>