An API-sourced live search that reached search.list has spent 100 units (the client records them
before it reads the status), so it keeps its daily slot: refunding it let a bogus cursor spend the
shared budget without ever counting against the cap. A failure before the call still gives the slot
back.
Every refund is rationed too (5 an hour per user and list): a cursor is a free string, and a request
built to fail would otherwise scrape YouTube from the server without end.
The API source asks the budget again right before search.list, under one process lock with the
call: checked apart, searches sent together at the last 100 units all passed and all spent.
Checked first and logged after search.list, requests sent together at the
last free slot all passed, and each spent 100 units of the shared budget.
Every live search now claims its slot (quota.claim_action) whatever the
source, and gives it back when it showed nothing. The cap counts the
zero-unit claims only, so search.list's own spend event is accounting,
not a second slot. log_action, the unlocked writer, goes.
Tests: the API source reads one page per request, is refused before the
call when the budget cannot pay, counts one slot per search and refunds a
failed one; the lock test now proves the count happens after the lock.
A related list's cursor cost nothing, and a cursor is a free string: a replayed one read and
enriched without end. Every request now takes a slot of the user's daily cap — taken under a lock
before the work (`quota.claim_action`), so requests sent together cannot all pass the last free
one, and given back when the request fails outright (`quota.refund_action`). The live search's
scrape source takes its slots the same way.
A limit of 0 turns the feature off: a distinct 409 `related_disabled` / `search_disabled`, and
`/api/me` says `related_enabled` / `search_enabled` so the UI can leave it out.
A videos.list that fails no longer reads as an empty page: `ingest_candidates` raises, and the
search and the related list answer the refusal (the shared budget spent says "quota") instead of
"no results". The two routes' page loops are one (`_gather`).
`clear` deletes only what the caller found: a related list's rows carry no find, and any user
could name them.
peter