[SatsAndSports]

Summary

PR1 of the client funding refactor, following merged #156.

• Add a pure ordinary-control/channel reducer. One Idle / Working / Submitting / AwaitingResponse slot owns main-client response attribution, replacing the FIFO plus separate in-flight flag.
• Classify responses without mutation and commit only after wallet/status validation. Share pure response checks with ControlExchange, which remains available for pipelined harnesses.
• Separate channel acquisition/reservation from linking. Optimistic selection of B retains previous A until the outcome; rejected replacement restores A unless independently evicted. Keep release advisories through outstanding operations and clean up all reservation roles on termination.
• Extract a pure funding strategy and intent/effect boundary. Retain the 250 ms timer and default target/minimum-topup and exhaustion policy. Busy ordinary operations suppress policy evaluation; funded idle evaluations use only task-owned state and atomic counters.
• Keep heartbeat/Ping/Pong and data forwarding outside the reducer. Preserve durable signed-payment handling and existing response-time wallet validation; the database-read optimization is PR2.
• Update architecture, payment, wallet, and contributor documentation.

Coverage

• Ordinary serialization and independent advisories/Pong
• Nonmutating response validation, wrong-channel/wrong-balance/short-paid rejection
• Policy can pay while unpaused or wait while paused
• Replacement success/rejection, previous-channel eviction and release
• Acquired reservation exclusivity and release without linking
• Failed link preparation releases the candidate and clears excluded retry intent
• Counting-wallet executor test: zero wallet calls during funded idle ticks and while each ordinary request type is pending

Verification

• cargo fmt --all
• make lint
• cargo test: full workspace passed, including 173 relay integration tests
• After final retry-preparation cleanup: make lint and cargo test -p monad-client --lib session_driver (67 passed)
• git diff --check

No wire, YAML, or database schema changes. Opened after local verification; CI is intentionally not awaited.