add pipeline task system, agentic music tasks, copy buttons, and pi-bridge cleanup

- Pipeline mode: new task mode that chains agentic tasks sequentially with
  foreach/subdirectory iteration and skip_if conditions
- Pipeline executor backend (WebSocket at /api/tasks/pipeline/ws) with
  support for both Pi and Claude Code models
- Frontend PipelineRunner component with step progress, streaming output,
  and aggregate cost tracking
- New agentic tasks: prepare-discography, fetch-album-info, build-discography
  (pipeline combining both)
- Seed parser extended to handle pipeline steps in frontmatter config
- CopyButton component added to assistant bubbles, error bubbles, and
  tool input/output sections
- Removed obsolete SearXNG/Apify/browser relay code from pi-bridge

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

seed/tasks/fetch-album-info/TASK.md

@@ -0,0 +1,97 @@
+---
+name: Fetch Album Info
+description: Search the web for album information and save a detailed info file.
+version: 1
+mode: agentic
+triggers:
+  - type: directory
+inputs:
+  artist_name:
+    type: string
+    description: Artist name
+    autofill: entry_name
+  album_name:
+    type: string
+    description: Album name
+    autofill: entry_name
+---
+
+# Fetch Album Info
+
+You are given an artist name and album name. Your job is to find comprehensive information about this album from the web.
+
+## Process
+
+1. **Search** for the album using `web_search` with queries like `"<artist> <album> wikipedia"`, `"<artist> <album> musicbrainz"`, `"<artist> <album> allmusic"`.
+2. **Fetch** the most relevant pages using `web_fetch` to extract detailed information.
+3. **Cross-reference** multiple sources to get the most accurate and complete data.
+4. **Download** the front cover image and save it as `cover.{ext}` (matching the image format, e.g. `cover.jpg`) in the target directory. Overwrite if it already exists.
+5. **Save** the result as an `album-info.md` file in the target directory (provided in Context).
+
+## Information to collect
+
+- **Artist** name (canonical/correct spelling)
+- **Album** title (canonical/correct spelling)
+- **Release year** (original release)
+- **Genre(s)** and subgenres
+- **Label** / record company
+- **Tracklist** — for each track: number, title, duration. For multi-disc releases, organize by disc.
+- **Total duration**
+- **Front cover image URL** — find the highest quality cover art URL available (Wikipedia, MusicBrainz cover art archive)
+- **Credits** — producer, engineer, notable musicians (if available)
+- **Additional notes** — compilation info, remaster details, notable facts
+
+## Output format
+
+Write a markdown file named `album-info.md` in the **target directory** (from Context) with this structure:
+
+```markdown
+# Artist — Album Title
+
+![Cover](url-to-cover-image)
+
+| Field | Value |
+|-------|-------|
+| Artist | ... |
+| Album | ... |
+| Year | ... |
+| Genre | ... |
+| Label | ... |
+| Duration | ... |
+
+## Tracklist
+
+### Disc 1
+| # | Title | Duration |
+|---|-------|----------|
+| 1 | ... | 0:00 |
+
+### Disc 2
+...
+
+## Credits
+- Producer: ...
+- ...
+
+## Notes
+...
+```
+
+If there is only one disc, omit the "Disc 1" heading and just use a flat tracklist.
+
+## Cover art download
+
+Once you have a cover image URL, download it to the target directory using curl:
+```
+curl -sL -o "<target_dir>/cover.<ext>" "<image_url>"
+```
+Use the correct extension based on the image format (jpg, png, etc.). Overwrite any existing file.
+In the `album-info.md`, keep the original remote URL in the image tag: `![Cover](<original_url>)`.
+
+## Important
+
+- Prefer Wikipedia for context, genre classification, credits, and tracklist data.
+- Use MusicBrainz / Cover Art Archive for high-quality cover image URLs and precise edition identification.
+- Use AllMusic as an additional source for credits and reviews.
+- If information conflicts between sources, prefer Wikipedia for metadata and MusicBrainz for tracklist data.
+- Do NOT make up information. If something is not found, omit it.