Add navidrome skill for Subsonic API playlist curation

Distilled from tonight's session building SUB/WAVE anchor-playlist
shows by hand: a CLI (search/artist/album/playlist get/create/replace/
add/remove) plus a playlist-audit command that flags accidental
full-album dumps, replacing the one-off curl/Python snippets used
throughout. SKILL.md documents the gotchas hit along the way
(case-sensitive artist matching, deluxe-reissue duplicate tracks,
createPlaylist's full-replace semantics) and this session's curation
conventions (15-20 tracks/artist, prefer playlistStrict).

Claude-Session: https://claude.ai/code/session_01L7Rwa6guD5wK8F8tWQwcJX

.claude/skills/navidrome/SKILL.md

@@ -0,0 +1,84 @@
+---
+name: navidrome
+description: Query and edit the Navidrome music library/playlists (search artists/albums, inspect or build playlists, audit for accidental full-album dumps). Use for any SUB/WAVE anchor-playlist curation work or general Navidrome library lookups.
+---
+
+# Navidrome (Subsonic API)
+
+A CLI wrapper (`navidrome_api.py`, in this skill's directory) around Navidrome's
+Subsonic API, distilled from a long session of building SUB/WAVE anchor-playlist
+shows by hand. Use it instead of writing one-off `curl`/Python snippets — every
+gotcha below was hit at least once doing it the ad-hoc way.
+
+## Setup
+
+Auth/URL come from `/srv/subwave/state/setup-config.json` (world-readable),
+already pointed at `navidrome:4533` — the script rewrites that host to
+`localhost` for you. No flags needed for auth.
+
+Run it as: `python3 .claude/skills/navidrome/navidrome_api.py <command> ...`
+
+## Commands
+
+```
+search <query> [--artists N] [--albums N] [--songs N]   # raw multi-type search
+artist <name>                                            # albums + track counts for one artist
+album <artist> <album>                                   # track ids for one album
+playlists                                                 # list all playlists (id, count, name)
+playlist get <id>                                         # dump entries
+playlist create <name> --ids id1,id2,...                  # new playlist
+playlist replace <id> --ids id1,id2,...                   # FULL REPLACE of contents
+playlist add <id> --ids id1,id2,...                        # append in place
+playlist remove <id> --ids id1,id2,...                     # remove by id, in place
+playlist audit <id> [--min-size N]                         # full-album-dump check (see below)
+```
+
+## Gotchas learned the hard way
+
+- **Artist name casing is inconsistent and case-sensitive matching silently
+  drops real hits.** `eels` is lowercase, `CAKE` is uppercase, most others are
+  title-case. A naive `artist["name"] == "Eels"` filter returns "not found" even
+  though the artist is right there. `artist`/`album` in this script already do
+  case-insensitive exact matching — don't re-derive this bug with a fresh `curl`.
+
+- **An artist with 0 albums from `getArtist` isn't necessarily absent** — it
+  may only have loose tracks scattered across compilations (soundtrack/box-set
+  albums credited to "Various Artists"). Fall back to `search3` with a high
+  `songCount` and filter by exact artist name (the `artist` command does this
+  automatically when it finds zero grouped albums).
+
+- **Reissues/deluxe editions duplicate the base album's tracks under a
+  different album name** (`Doolittle` vs `Doolittle 25`, `Bricks Are Heavy` vs
+  a live/remix bonus disc, etc). When curating, pick tracks from ONE edition —
+  check `album` output for suspiciously large counts before assuming it's all
+  distinct songs.
+
+- **`createPlaylist` with `playlistId` set REPLACES the entire contents** —
+  it is not additive. Use `playlist replace` only when you intend to overwrite
+  everything (e.g., rebuilding after a curation pass). Use `playlist add` /
+  `playlist remove` for incremental edits to an existing playlist.
+
+- **No native "remove by id" in the Subsonic API** — `playlist remove` here
+  works by reading the current entries, filtering out the unwanted ids in
+  Python, then doing a full `replace`. This is safe (order-preserving for
+  everything you keep) but means a remove is really a replace under the hood.
+
+- **`playlist audit`'s "FULL ALBUM" flag is a signal, not a verdict.** A
+  genuinely short album (say, 10 tracks) will always show `10/10` with nothing
+  left to trim, and an artist you were explicitly told to go "heavy" on is
+  fine full. Use it to know where to *look*, then use judgment (or ask) before
+  trimming.
+
+## Curation conventions established this session
+
+- Default to **~15–20 tracks per artist** for an anchor playlist, not a full
+  discography — unless the user explicitly asks for heavier coverage of a
+  specific artist ("heavy Nirvana", "triple that, focusing on XTC").
+- Prefer **`playlistStrict: true`** on SUB/WAVE shows with a pinned anchor
+  playlist. Soft-anchor (`playlistStrict: false`) was tried and rolled back
+  station-wide after live testing showed the playlist rarely won picks over
+  the genre/mood fallback pool, and the fallback's unfiltered "explore" source
+  could drift the show off-genre (see `subwave/bug-report-soft-anchor-drift.md`).
+- Cross-show duplicate tracks are fine for these anchor-genre shows (the
+  no-duplicate rule only applies to the historical radio-chart recreation
+  shows) — don't spend time deduplicating against other playlists unless asked.