feat(overlay): add in-app changelog modal

- Add a changelog modal opened from tray "View Changelog" or the update notification's "What's New" button; renders in-player or in its own window like the help modal
- Fetch changelog from the newest published release so newer-than-installed notes are visible, falling back to the bundled CHANGELOG.md on failure
- Group versions by minor line (current expanded, older folded), badge the installed version, tag newer ones "New"
- Support J/K/arrow navigation, Enter to fold/unfold, R to refetch, Esc to close
- Add changelog parsing/semver-compare utils and changelog IPC channel/runtime; bundle CHANGELOG.md into packaged builds
- Replace release/release-notes.md with changes/changelog-modal.md changeset entry

src/core/utils/changelog-parse.ts

@@ -0,0 +1,123 @@
+import type { ChangelogEntry, ChangelogItem, ChangelogSection } from '../../types/changelog';
+
+const VERSION_HEADING = /^##\s+v(\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?)\s*(?:\(([^)]*)\))?\s*$/;
+const SECTION_HEADING = /^###\s+(.+?)\s*$/;
+const BULLET = /^(\s*)[-*]\s+(.*)$/;
+
+/**
+ * Entries are grouped by `major.minor` so the whole current minor line renders
+ * expanded, matching how docs-site/changelog.md splits current vs previous.
+ */
+export function resolveChangelogGroupKey(version: string): string {
+  const match = version.match(/^(\d+)\.(\d+)/);
+  if (!match) return version;
+  return `${match[1]}.${match[2]}`;
+}
+
+/**
+ * Parses the repo CHANGELOG.md into version entries. Bullets keep their inline
+ * markdown and their nesting: older entries group related notes under a bold
+ * lead bullet with indented children, and flattening them loses that structure.
+ */
+export function parseChangelog(markdown: string): ChangelogEntry[] {
+  const entries: ChangelogEntry[] = [];
+  let entry: ChangelogEntry | null = null;
+  let section: ChangelogSection | null = null;
+  let internal = false;
+  // Open bullets from outermost to innermost, used to place the next bullet.
+  let openItems: Array<{ indent: number; item: ChangelogItem }> = [];
+
+  function startSection(heading: string): void {
+    section = { heading, items: [], internal };
+    openItems = [];
+    entry?.sections.push(section);
+  }
+
+  function addBullet(indent: number, text: string): void {
+    if (!section) {
+      // Bullets before any "###" heading (older entries) land in a generic group.
+      startSection('Changes');
+    }
+    const item: ChangelogItem = { text, children: [] };
+
+    while (openItems.length > 0 && (openItems[openItems.length - 1]?.indent ?? 0) >= indent) {
+      openItems.pop();
+    }
+    const parent = openItems[openItems.length - 1];
+    if (parent) {
+      parent.item.children.push(item);
+    } else {
+      section?.items.push(item);
+    }
+    openItems.push({ indent, item });
+  }
+
+  function appendContinuation(text: string): void {
+    const current = openItems[openItems.length - 1];
+    if (!current) return;
+    current.item.text = `${current.item.text} ${text}`;
+  }
+
+  for (const rawLine of markdown.split(/\r?\n/)) {
+    const line = rawLine.trimEnd();
+    const trimmed = line.trim();
+
+    const versionMatch = trimmed.match(VERSION_HEADING);
+    if (versionMatch) {
+      const version = versionMatch[1] ?? '';
+      entry = {
+        version,
+        date: versionMatch[2]?.trim() ?? '',
+        groupKey: resolveChangelogGroupKey(version),
+        sections: [],
+      };
+      entries.push(entry);
+      section = null;
+      internal = false;
+      openItems = [];
+      continue;
+    }
+
+    if (!entry) continue;
+
+    if (trimmed.startsWith('<details')) {
+      internal = true;
+      section = null;
+      openItems = [];
+      continue;
+    }
+    if (trimmed.startsWith('</details')) {
+      internal = false;
+      section = null;
+      openItems = [];
+      continue;
+    }
+    if (trimmed.startsWith('<summary')) continue;
+
+    const sectionMatch = trimmed.match(SECTION_HEADING);
+    if (sectionMatch) {
+      startSection(sectionMatch[1] ?? '');
+      continue;
+    }
+
+    const bulletMatch = line.match(BULLET);
+    if (bulletMatch) {
+      addBullet((bulletMatch[1] ?? '').length, bulletMatch[2] ?? '');
+      continue;
+    }
+
+    // A blank line ends the current bullet run; an indented non-bullet line is a
+    // wrapped continuation of the bullet above it.
+    if (!trimmed) {
+      continue;
+    }
+    if (/^\s/.test(line)) {
+      appendContinuation(trimmed);
+    }
+  }
+
+  return entries.map((item) => ({
+    ...item,
+    sections: item.sections.filter((entrySection) => entrySection.items.length > 0),
+  }));
+}