feature: brokerage order polling service - #9696

…ge queue

- BrokerageMessageQueue owns the lock, buffer and dispatch, raised through a MessageReceived event
- BrokerageConcurrentMessageHandler<T> becomes a thin wrapper with the same public API
- add RegisterMessageType<TMessage> and a generic HandleNewMessage<TMessage>, so a second message source can queue behind the same lock instead of a separate, independent one
- add BrokerageMessageQueueTests covering the shared lock, an unmatched message type, and a registered second type

- abstract BrokerageOrderPollingService with per-order-id and all-orders modes: watch registry, state compare, watch timeout, repeated-failure warning
- plugins seed the registry before Start, so the first sweep repeats nothing the stream already reported
- ADR: seed-before-start handover and the survey of streaming plugins that fit it
- tests: 25 polling service, 4 message queue

- guard, buffered-message processing, one seed per open Lean order, Start - in the only safe order
- both callbacks optional and nullable

- add non-generic BrokerageConcurrentMessageHandler with per-type Register, reusing the generic handler by composition
- restore BrokerageConcurrentMessageHandler<T> to master and drop BrokerageMessageQueue
- service constructor takes the handler, registers ProcessOrderState and routes the states; SeedAndStart drains the handler internally
- update the ADR wiring, seed-before-start and risk sections, and note the CharlesSchwab pilot

- a plain place watches the main id; the first sweep assigns the leg ids by symbol and reports the submit through the diff
- the assignment is one shared method with the stream's OrderAccepted and releases the three minute place wait in both modes
- the pilot note lists the leg id assignment and the replace reporting as what stays in the plugin

- watch replacement watches the new id of a replace and drops the replaced one
- the diff's first state for a marked id reports the update submit
- the new id starts with no fill state; carry-over brokers seed instead

- survey of nine sibling plugins' update paths, checked line by line
- replacement watch design, the no-wait rule, and the rejected event reuse

- status entries: pilot verified live on real accounts; public.com is the second plugin on the service
- pricing text matches what shipped: public keeps its change-of-average recovery inside its mapping
- rollout item 3 trimmed to the one intentional behavior change

- protected create overloads pick the per-order-id or all-orders mode by the read callback
- the service events forward onto the brokerage events; a virtual method owns the not-acknowledged warning
- dispose covers the created service

- status entries for the wiring seam and the third plugin
- cross-zero section: leg chaining from the read and the fill-offset seed
- wiring examples moved onto the create seam
- testing section: live capture first, recorded mock data, offline checklist

- fixtures play the transaction handler: write each reported status back onto the lean order and assert in live cycle order

- rename SeedAndStart(seed) to the Start(preLoadOpenOrders) overload
- add BrokerOrderState constructors, one overload takes the message without fills
- trace the wired service with its intervals and the pre-load counts

- record public.com's live-first testing run and the offline checklist additions
- tradier reads per id and has draft pr; stale refs and tenses fixed
- the pre-loading start, the state constructors and the price-recovery note

…time

- rename BrokerOrderState to BrokerageOrderSnapshot across the service and tests
- drop the property-fill constructor, every builder goes through the constructors
- timeUtc is nullable in the constructors and defaults to DateTime.UtcNow
- shorten the snapshot xml docs

- SingleOrderPollingService and BulkOrdersPollingService, base takes the Base prefix
- callbacks are getBrokerageOrderById and getAllBrokerageOrders; watchTimeout is notificationTimeout
- both mode classes chain three constructors instead of optional parameters
- defaults read 3 * 1000 and 60 * 1000 ms; usage remarks with a wiring example on both modes