Pumps live driver OnDataChange notifications into CachedTagUpstreamSource so
ctx.GetTag in user scripts sees the freshest driver value. The last missing piece
between #243 (composition kernel) and #246 (Program.cs wire-in).
## DriverSubscriptionBridge
IAsyncDisposable. Per DriverFeed: groups all paths for one ISubscribable into a
single SubscribeAsync call (consolidating polled drivers' work + giving
native-subscription drivers one watch list), keeps a per-feed reverse map from
driver-opaque fullRef back to script-side UNS path, hooks OnDataChange to
translate + push into the cache. DisposeAsync awaits UnsubscribeAsync per active
subscription + unhooks every handler so events post-dispose are silent.
Empty PathToFullRef map → feed skipped (no SubscribeAsync call). Subscribe failure
on any feed unhooks that feed's handler + propagates so misconfiguration aborts
bridge start cleanly. Double-Start throws InvalidOperationException; double-Dispose
is idempotent.
OTOPCUA0001 suppressed at the two ISubscribable call sites with comments
explaining the carve-out: bridge is the lifecycle-coordinator for Phase 7
subscriptions (one Subscribe at engine compose, one Unsubscribe at shutdown),
not the per-call hot-path. Driver Read dispatch still goes through CapabilityInvoker
via DriverNodeManager.
## Tests — 9 new = 29 Phase 7 tests total
DriverSubscriptionBridgeTests covers: SubscribeAsync called with distinct fullRefs,
OnDataChange pushes to cache keyed by UNS path, unmapped fullRef ignored, empty
PathToFullRef skips Subscribe, DisposeAsync unsubscribes + unhooks (post-dispose
events don't push), StartAsync called twice throws, DisposeAsync idempotent,
Subscribe failure unhooks handler + propagates, ctor null guards.
## Phase 7 production wiring chain status
- #243✅ composition kernel
- #245✅ scripted-alarm IReadable adapter
- #244✅ this — driver bridge
- #246 pending — Program.cs Compose call + SqliteStoreAndForwardSink lifecycle
- #240 pending — live E2E smoke (unblocks once #246 lands)
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