Design doc for a new `absdy` provider mounted at `/abs` that browses,
searches, and plays audiobooks from a self-hosted audiobookshelf server.
Shaped on the fyyd provider: an `Abs` reqwest seam faked in tests, an
in-memory per-library search-term store, and a `library -> book -> tracks`
tree with a per-library `search` subtree.
Grounded live against the test server: bearer auth for browse, `?token=`
query auth plus HTTP range (206) on the file endpoint, so a track's stream
URL is fully derivable from its path with no extra call. The embedded token
and the api_key are secrets, redacted from logs/Debug (hard rule).
Also gitignores the abs-api-key file so the JWT never lands in a commit.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>