feat: scaffold Tauri v2 + Svelte 5 project with base layout and utilities

Co-authored-by: Cursor <cursoragent@cursor.com>

chat-summaries/2026-09-21_10-22-brainstorm-and-plan-video-clipper-summary.md

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+# Video Clipper — Brainstorming & Implementation Plan
+
+**Date:** 2026-09-21 10:22
+**Task:** Brainstormed the design and wrote a comprehensive implementation plan for a macOS GUI video clipper app.
+
+## Task Description
+
+Designed and planned a macOS GUI app ("Video Clipper") that lets users paste a YouTube URL, scrub a timeline, mark clip boundaries, and export clips — without manually downloading the video first. Like LosslessCut, but for online videos.
+
+## Changes Made
+
+### Design Spec (`docs/superpowers/specs/2026-09-21-video-clipper-design.md`)
+- Brainstormed tech approach: chose **Tauri v2 + Svelte 5** over Swift/SwiftUI and Python/Qt
+- Defined architecture: Rust backend (subprocess orchestration), Svelte frontend (Canvas timeline), external CLI tools (ffmpeg, yt-dlp)
+- Designed hybrid playback: stream immediately for preview, download in background for export
+- Designed 4-layer Canvas timeline: thumbnails → waveform → clip markers → controls
+- Researched YouTube 2026 auth landscape: cookies + PO Token + JS runtime required
+- Added three features to MVP during review: waveform visualization, thumbnail strip, cookie/auth support
+- Defined complete data model, keyboard shortcuts (NLE-style), export flow, edge cases
+
+### Implementation Plan (`docs/superpowers/plans/2026-09-21-video-clipper.md`)
+12 tasks with TDD approach, exact file paths, complete code, and test code:
+
+1. **Project Scaffolding** — Tauri v2 + Svelte 5 scaffold, plugins, layout shell, utility functions
+2. **Dependency Manager + Setup Wizard** — Check ffmpeg/yt-dlp/deno/PO-token-plugin, guided install
+3. **Preferences Store** — Cookie source (Firefox default), output directory, persistence
+4. **Video Resolver + URL Input + Video Player** — yt-dlp metadata/stream URL, paste-to-play pipeline
+5. **Download Manager + Status Bar** — Background yt-dlp download with progress channel
+6. **Timeline Core** — Canvas renderer, coordinate mapping, playhead, scrub, zoom
+7. **Clip Management** — I/O marking, clip CRUD store, timeline markers, draggable handles, ClipList
+8. **Transport Controls + Keyboard Shortcuts** — All playback controls, J/K/L shuttle, all hotkeys
+9. **Keyframe Index** — ffprobe extraction, keyframe/frame navigation
+10. **Waveform** — ffmpeg audio peak extraction, Canvas rendering with zoom aggregation
+11. **Thumbnails** — ffmpeg frame extraction, sprite sheets, adaptive-density Canvas rendering
+12. **Clip Export + Export Dialog** — Lossless/precise/merged ffmpeg pipeline, full export UI
+
+## Key Decisions
+
+- **Tauri v2 + Svelte 5** chosen over Swift/SwiftUI for natural Canvas/timeline UI building
+- **Firefox cookies default** — only browser where `--cookies-from-browser` reliably works in 2026
+- **bgutil-ytdlp-pot-provider** plugin required for YouTube PO Token generation
+- **Tauri Channels** (not events) for streaming progress data — strongly typed, optimized for throughput
+- **Static placeholder** for waveform/thumbnails before download completes (not progressive)
+- **Sprite sheet** approach for thumbnails to minimize image load overhead
+
+## Lessons Learned
+
+- YouTube in 2026 requires a 3-part auth chain: cookies + PO Token provider plugin + JS runtime. Just `--cookies-from-browser` alone is insufficient.
+- Chrome 127+ broke cookie decryption for external tools — Firefox is the only reliable browser for `--cookies-from-browser`.
+- Tauri v2 Channels (`tauri::ipc::Channel`) are the recommended way to stream data from Rust→frontend, not the event system (which is JSON-only and not designed for throughput).
+- `yt-dlp -v` with a URL shows `[debug] Extractor Plugins: GetPOT` to verify the PO token plugin is installed — there's no dedicated `--list-plugins` flag.
+
+## Follow-up Items
+
+- Stream URL re-resolution on playback error (noted in plan self-review but not a dedicated task)
+- Future features documented in spec: local file support, quality selection, save/load projects, batch processing, cross-platform