Resident agents call GET /api/exploration/patrol once per cycle to see
every running production-line campaign that opted into exploration
(seed set present), the new results since the last watermark (reusing
campaign report aggregation), and the remaining exploration budget.
The watermark advances after each call so subsequent calls only report
increments; accelerated and terminal campaigns are excluded.
v0.9 ticket 01. Independent exploration_sessions/exploration_messages
entities (never merged into EvalRun, keeping ADR-0001/0002 semantics
intact): create/message/close APIs forward virtual-user messages through
the target's real channel, persist both parties' rows with latency, and
close with a whitelist-normalized experience record. Budget enforcement
is a platform ledger — sessions per window, turns per session, and
session interval overruns return 409 with readable reasons; accelerated
lines accept manual sessions only. Messages delivered but unanswered
still consume a turn so timeouts cannot bypass the budget.
