feat(project-editor): syntax-highlighted code editor for HTML raw mode

- shared app-code-editor: overlay textarea + highlighted <pre> layer,
  no external dependency (Monaco/CodeMirror)
- tokenizeCss: selector/property/value/string/comment/at-rule aware,
  brace-depth state machine
- tokenizeHtml: tags + comments colored, delegates <style> block content
  to tokenizeCss (that's where static-page CSS is actually authored)
- marketplace-html-editor raw-code mode now uses app-code-editor instead
  of a plain textarea

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/shared/ui/code-editor/code-editor.component.html

@@ -0,0 +1,14 @@
+<div class="code-editor" [class.code-editor--invalid]="invalid()" [class.code-editor--focused]="focused()">
+  <pre #highlightLayer class="code-editor-highlight" [attr.rows]="rows()"><code [innerHTML]="highlighted()"></code></pre>
+  <textarea
+    #textarea
+    class="code-editor-input"
+    [rows]="rows()"
+    spellcheck="false"
+    [value]="value()"
+    (input)="onInput($event)"
+    (scroll)="syncScroll()"
+    (focus)="focused.set(true)"
+    (blur)="focused.set(false)"
+  ></textarea>
+</div>

src/app/shared/ui/code-editor/code-editor.component.scss

@@ -0,0 +1,87 @@
+:host {
+  display: block;
+}
+
+.code-editor {
+  position: relative;
+  border: 1px solid var(--border-color, #d3dad9);
+  border-radius: 10px;
+  overflow: hidden;
+}
+
+.code-editor--invalid {
+  border-color: var(--error-color, #991b1b);
+}
+
+.code-editor--focused {
+  border-color: #497671;
+  box-shadow: 0 0 0 2px rgba(73, 118, 113, 0.15);
+}
+
+.code-editor-highlight,
+.code-editor-input {
+  margin: 0;
+  padding: 10px 12px;
+  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
+  font-size: 13px;
+  line-height: 1.5;
+  white-space: pre;
+  overflow: auto;
+}
+
+.code-editor-highlight {
+  position: absolute;
+  inset: 0;
+  pointer-events: none;
+  color: var(--text-primary, #1e3c38);
+  background: #fbfcfc;
+}
+
+.code-editor-input {
+  position: relative;
+  width: 100%;
+  border: 0;
+  resize: vertical;
+  background: transparent;
+  color: transparent;
+  caret-color: var(--text-primary, #1e3c38);
+}
+
+.code-editor-input::selection {
+  background: rgba(73, 118, 113, 0.25);
+}
+
+:global(.cm-comment) {
+  color: #7f8c8d;
+  font-style: italic;
+}
+
+:global(.cm-string) {
+  color: #2f7d5e;
+}
+
+:global(.cm-tag) {
+  color: #6d3fa8;
+}
+
+:global(.cm-selector) {
+  color: #b2452f;
+  font-weight: 600;
+}
+
+:global(.cm-property) {
+  color: #1f6f8b;
+}
+
+:global(.cm-value) {
+  color: #1e3c38;
+}
+
+:global(.cm-keyword) {
+  color: #6d3fa8;
+  font-weight: 600;
+}
+
+:global(.cm-punct) {
+  color: var(--text-secondary, #5f6e6a);
+}

src/app/shared/ui/code-editor/code-editor.component.ts

@@ -0,0 +1,39 @@
+import { ChangeDetectionStrategy, Component, ElementRef, ViewChild, computed, input, output, signal } from '@angular/core';
+import { renderHighlighted, tokenizeCss, tokenizeHtml } from './code-highlight';
+
+export type CodeEditorLanguage = 'html' | 'css';
+
+@Component({
+  selector: 'app-code-editor',
+  standalone: true,
+  templateUrl: './code-editor.component.html',
+  styleUrl: './code-editor.component.scss',
+  changeDetection: ChangeDetectionStrategy.OnPush
+})
+export class CodeEditorComponent {
+  readonly value = input('');
+  readonly language = input<CodeEditorLanguage>('html');
+  readonly rows = input(10);
+  readonly invalid = input(false);
+
+  readonly valueChange = output<string>();
+
+  @ViewChild('textarea', { static: true }) private textarea!: ElementRef<HTMLTextAreaElement>;
+  @ViewChild('highlightLayer', { static: true }) private highlightLayer!: ElementRef<HTMLElement>;
+
+  protected readonly highlighted = computed(() => {
+    const tokens = this.language() === 'css' ? tokenizeCss(this.value()) : tokenizeHtml(this.value());
+    return renderHighlighted(tokens) + '\n';
+  });
+
+  protected readonly focused = signal(false);
+
+  protected onInput(event: Event): void {
+    this.valueChange.emit((event.target as HTMLTextAreaElement).value);
+  }
+
+  protected syncScroll(): void {
+    this.highlightLayer.nativeElement.scrollTop = this.textarea.nativeElement.scrollTop;
+    this.highlightLayer.nativeElement.scrollLeft = this.textarea.nativeElement.scrollLeft;
+  }
+}

src/app/shared/ui/code-editor/code-highlight.ts

@@ -0,0 +1,167 @@
+export interface HighlightToken {
+  text: string;
+  cls: string | null;
+}
+
+function escapeHtml(text: string): string {
+  return text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+}
+
+/**
+ * Single-pass CSS tokenizer. Tracks brace depth + a selector/property/value
+ * mode so the same bare-word token (e.g. `color`) is classified differently
+ * depending on where it sits, without a full CSS parser.
+ */
+export function tokenizeCss(css: string): HighlightToken[] {
+  const tokens: HighlightToken[] = [];
+  let i = 0;
+  let braceDepth = 0;
+  let mode: 'selector' | 'property' | 'value' = 'selector';
+
+  while (i < css.length) {
+    if (css.startsWith('/*', i)) {
+      const end = css.indexOf('*/', i + 2);
+      const stop = end === -1 ? css.length : end + 2;
+      tokens.push({ text: css.slice(i, stop), cls: 'cm-comment' });
+      i = stop;
+      continue;
+    }
+    const ch = css[i];
+    if (ch === '"' || ch === "'") {
+      let j = i + 1;
+      while (j < css.length && css[j] !== ch) {
+        if (css[j] === '\\') j++;
+        j++;
+      }
+      j = Math.min(j + 1, css.length);
+      tokens.push({ text: css.slice(i, j), cls: 'cm-string' });
+      i = j;
+      continue;
+    }
+    if (ch === '{') {
+      tokens.push({ text: '{', cls: 'cm-punct' });
+      braceDepth++;
+      mode = 'property';
+      i++;
+      continue;
+    }
+    if (ch === '}') {
+      tokens.push({ text: '}', cls: 'cm-punct' });
+      braceDepth = Math.max(0, braceDepth - 1);
+      mode = braceDepth > 0 ? 'property' : 'selector';
+      i++;
+      continue;
+    }
+    if (ch === ':' && braceDepth > 0 && mode === 'property') {
+      tokens.push({ text: ':', cls: 'cm-punct' });
+      mode = 'value';
+      i++;
+      continue;
+    }
+    if (ch === ';') {
+      tokens.push({ text: ';', cls: 'cm-punct' });
+      mode = braceDepth > 0 ? 'property' : mode;
+      i++;
+      continue;
+    }
+    if (ch === ',') {
+      tokens.push({ text: ',', cls: 'cm-punct' });
+      i++;
+      continue;
+    }
+    let j = i;
+    while (j < css.length && !'{}:;,"\''.includes(css[j]) && !css.startsWith('/*', j)) {
+      j++;
+    }
+    if (j === i) {
+      j = i + 1;
+    }
+    const text = css.slice(i, j);
+    const cls = mode === 'selector' ? 'cm-selector' : mode === 'property' ? (/^\s*@/.test(text) ? 'cm-keyword' : 'cm-property') : 'cm-value';
+    tokens.push({ text, cls });
+    i = j;
+  }
+  return tokens;
+}
+
+/** Colors a whole `<tag ...>` as one token, except quoted attribute values (strings). */
+function tokenizeTag(tagText: string): HighlightToken[] {
+  const tokens: HighlightToken[] = [];
+  const stringRe = /"[^"]*"|'[^']*'/g;
+  let last = 0;
+  let match: RegExpExecArray | null;
+  while ((match = stringRe.exec(tagText))) {
+    if (match.index > last) {
+      tokens.push({ text: tagText.slice(last, match.index), cls: 'cm-tag' });
+    }
+    tokens.push({ text: match[0], cls: 'cm-string' });
+    last = stringRe.lastIndex;
+  }
+  if (last < tagText.length) {
+    tokens.push({ text: tagText.slice(last), cls: 'cm-tag' });
+  }
+  return tokens;
+}
+
+/**
+ * HTML tokenizer: comments + tags get coarse coloring (fine-grained for
+ * quoted attribute values), plain text stays uncolored. Content inside
+ * `<style>...</style>` is delegated to the CSS tokenizer, since that is
+ * where marketplace static pages actually author CSS.
+ */
+export function tokenizeHtml(html: string): HighlightToken[] {
+  const tokens: HighlightToken[] = [];
+  let i = 0;
+
+  while (i < html.length) {
+    if (html.startsWith('<!--', i)) {
+      const end = html.indexOf('-->', i + 4);
+      const stop = end === -1 ? html.length : end + 3;
+      tokens.push({ text: html.slice(i, stop), cls: 'cm-comment' });
+      i = stop;
+      continue;
+    }
+    if (html[i] === '<') {
+      let j = i + 1;
+      let inStr: string | null = null;
+      while (j < html.length) {
+        const ch = html[j];
+        if (inStr) {
+          if (ch === inStr) inStr = null;
+          j++;
+          continue;
+        }
+        if (ch === '"' || ch === "'") {
+          inStr = ch;
+          j++;
+          continue;
+        }
+        if (ch === '>') {
+          j++;
+          break;
+        }
+        j++;
+      }
+      const tagText = html.slice(i, j);
+      tokens.push(...tokenizeTag(tagText));
+      const isStyleOpenTag = /^<style(\s[^>]*)?>$/i.test(tagText);
+      i = j;
+      if (isStyleOpenTag) {
+        const closeIdx = html.toLowerCase().indexOf('</style', i);
+        const contentEnd = closeIdx === -1 ? html.length : closeIdx;
+        tokens.push(...tokenizeCss(html.slice(i, contentEnd)));
+        i = contentEnd;
+      }
+      continue;
+    }
+    let j = html.indexOf('<', i);
+    if (j === -1) j = html.length;
+    tokens.push({ text: html.slice(i, j), cls: null });
+    i = j;
+  }
+  return tokens;
+}
+
+export function renderHighlighted(tokens: HighlightToken[]): string {
+  return tokens.map(token => (token.cls ? `<span class="${token.cls}">${escapeHtml(token.text)}</span>` : escapeHtml(token.text))).join('');
+}