Content inspection and archive walks on seeding nodes (relay)

Inspection is split into prepare (database), probe (lib/content/probe:
downloads, decoding and parsing, no database) and apply (database).
worker:collection runs all three; seed:node with SEED_INSPECTORS leases
jobs from the same queues through the seed API (BullMQ manual leases),
fetches articles through the seed API and posts the probes back.

A node now needs only SEED_URL and SEED_TOKEN: the settings the app
requires but a node never uses get placeholders for seed:node.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

seed-node/node.env.example

@@ -1,34 +1,18 @@
-# --- Seed API: the orchestrator, and this node's token (`node ace seed:token <name>` on the indexer).
+# The seed API (the orchestrator) and this node's token (`node ace seed:token <name>` on the indexer).
 SEED_URL=https://seed.exp.sforum.nl
 SEED_TOKEN=sn_replace_me
-# Ranges worked on at once (about 0.4 CPU core each).
-SEED_CONNECTIONS=4
-# relay: headers come through the seed API, no news server account needed (the default).
-# direct: the node fetches with its own NNTP account; then fill in the NNTP_* lines below.
-SEED_FETCH=relay
 
-# --- Only for SEED_FETCH=direct: the NNTP account (counts against its connection and IP limits).
-NNTP_HOST=localhost
-NNTP_PORT=563
-NNTP_SECURE=true
-NNTP_USER=unused
-NNTP_PASSWORD=unused
+# Ranges seeded at once (about 0.4 CPU core each). 0: no seeding.
+SEED_CONNECTIONS=4
+# Content inspections and archive walks at once (CPU for decoding and parsing; articles come through the seed API).
+SEED_INSPECTORS=0
+
+# Optional: SEED_FETCH=direct seeds with this node's own NNTP account instead of through the seed API.
+# SEED_FETCH=direct
+# NNTP_HOST=news.eweka.nl
+# NNTP_PORT=563
+# NNTP_SECURE=true
+# NNTP_USER=
+# NNTP_PASSWORD=
 # Through a tunnel or proxy: the hostname the server's TLS certificate is for.
 # NNTP_TLS_SERVERNAME=news.eweka.nl
-
-# --- Required by the app's configuration, but unused on a seeding node (no database, Redis or web server).
-NODE_ENV=production
-TZ=UTC
-PORT=3333
-HOST=0.0.0.0
-LOG_LEVEL=info
-APP_KEY=unused-on-seed-nodes-unused-on-seed-nodes
-APP_URL=http://localhost:3333
-SESSION_DRIVER=memory
-DB_CONNECTION=pg
-DB_HOST=localhost
-DB_PORT=5432
-DB_USER=unused
-DB_DATABASE=unused
-REDIS_HOST=localhost
-REDIS_PORT=6379