chore(changelog): split release details into nested bullets

- Update changelog generation guidance and tests
- Reformat current release notes and document the new style

docs-site/changelog.md

@@ -10,9 +10,22 @@
 - **Prerelease Release Notes**: Prerelease notes now open with a "Changes since" section listing only what changed versus the previous beta/RC of the same version, above the cumulative highlights, and CI rejects prerelease tags whose committed notes were generated for a different beta/RC.
 
 **Fixed**
-- **Subtitle & Karaoke Duplication**: Typeset ASS karaoke and animated signs no longer flood the overlay, subtitle sidebar, immersion history, mining, or stats with glyph fragments, per-frame color phases, or repeated animation events. Lines are reconstructed once from their authored text and shown only while actually sung, with original word spacing preserved. Decorative layers (highlight sweeps, glow/shadow copies, symbol-font decoration, particle swarms, hidden or zero-scaled text) stay out of published text, while ordinary repeated dialogue, positioned signs, wrapped lyric rows, and multi-row CC-style blocks still display correctly. Embedded subtitle tracks on network-mounted (SMB/NFS) media are extracted and parsed again instead of falling back to live-text-only, restoring karaoke reconstruction, sidebar cues, and mining for releases that only ship subtitles inside the container. Secondary subtitles now go through the same deduplication pipeline as primary subtitles and no longer clip display after about four lines. Event-heavy karaoke files that previously stalled subtitle loading for several seconds now parse in well under a second.
-- **Character Dictionary Reliability**: Character dictionary generation, merged rebuilds, and imports no longer freeze the app on large dictionaries. Snapshot I/O, archive building, and image/name lookup caches moved off the UI's critical path. Dictionaries are reused instead of regenerated when MeCab finds no name splits, and cached portraits now restore correctly after the portrait index finishes loading post-tokenization. Desktop progress notifications on Linux AppImage installs now update in place instead of flickering, fixing a bug where the AppImage's bundled libraries broke the system notification helper.
-- **Overlay Startup & Modals**: Fixed several causes of the overlay getting stuck on "Overlay loading": the macOS window-tracking helper now targets macOS 12.0+ instead of requiring the build machine's exact macOS version (previously crashed on older systems like Ventura), and mpv IPC connection attempts now time out and retry, showing an actionable error if content still isn't ready after 30 seconds. Dedicated overlay modals are also prewarmed on macOS and Windows so shortcuts open them promptly, and on macOS reused modals and the stats window now open above fullscreen mpv on its current Space instead of jumping to another desktop.
+- **Subtitle & Karaoke Duplication**:
+  - Karaoke and animated signs are reconstructed once from their authored text and shown only while actually sung, with original word spacing preserved, instead of flooding the overlay, subtitle sidebar, immersion history, mining, or stats with glyph fragments, per-frame color phases, and repeated animation events.
+  - Decorative layers (highlight sweeps, glow/shadow copies, symbol-font decoration, particle swarms, hidden or zero-scaled text) stay out of published text, while ordinary repeated dialogue, positioned signs, wrapped lyric rows, and multi-row CC-style blocks still display correctly.
+  - Embedded subtitle tracks on network-mounted (SMB/NFS) media are extracted and parsed again instead of falling back to live-text-only, restoring karaoke reconstruction, sidebar cues, and mining for releases that only ship subtitles inside the container.
+  - Secondary subtitles go through the same deduplication pipeline as primary subtitles and no longer clip display after about four lines.
+  - Event-heavy karaoke files that previously stalled subtitle loading for several seconds now parse in well under a second.
+- **Character Dictionary Reliability**:
+  - Generation, merged rebuilds, and imports no longer freeze the app on large dictionaries; snapshot I/O, archive building, and image/name lookup caches moved off the UI's critical path.
+  - Dictionaries are reused instead of regenerated when MeCab finds no name splits.
+  - Cached portraits restore correctly after the portrait index finishes loading post-tokenization.
+  - Desktop progress notifications on Linux AppImage installs update in place instead of flickering, fixing a bug where the AppImage's bundled libraries broke the system notification helper.
+- **Overlay Startup & Modals**:
+  - The macOS window-tracking helper targets macOS 12.0+ instead of requiring the build machine's exact macOS version, fixing crashes on older systems like Ventura that left the overlay stuck on "Overlay loading".
+  - mpv IPC connection attempts time out and retry, showing an actionable error if content still isn't ready after 30 seconds.
+  - Dedicated overlay modals are prewarmed on macOS and Windows so shortcuts open them promptly.
+  - On macOS, reused modals and the stats window open above fullscreen mpv on its current Space instead of jumping to another desktop.
 - **Wayland File Drop**: Fixed native Wayland drag-and-drop from file managers such as Thunar, so subtitle and video files dropped on the visible overlay are resolved and forwarded to mpv.
 - **Windows Mouse Lag**: Fixed system-wide mouse lag on Windows while SubMiner is running, caused by the overlay's global mouse hook for click-through forwarding and by the mpv window tracker blocking the app on repeated PowerShell lookups.
 - **Sentence Mining Audio & Clips**: Sentence-audio generation no longer times out on slow network-mounted media with many subtitle/font streams (bounded FFmpeg probing, two-minute extraction budget, clearer error reporting), and mined audio/animated AVIF clips now capture the subtitle line that was actually mined by snapshotting the clip range at lookup time instead of reading live mpv state later.