Class ManualBufferTransfer<T>

Buffer with manual read control via trigger().

Capabilities: isInput, isOutput, isPushable, isPullable, isTriggerable

Mechanics:

1. push(data) — writes the value (overwrites the previous one)
2. trigger() — sets the _triggered flag to true
3. pull() — returns the value only if trigger() was called, otherwise returns undefined; extracts with cleanup (pop)

Difference from BufferTransfer:

• pull() returns data only after trigger()
• Implements a "lazy" read pattern: data is ready but not yielded until explicit permission

Use cases:

• Synchronizing reads with an external event
• Buffer with a data-readiness condition
• Step-by-step data processing in a pipeline