Added new documentation on FLOW

doc/usage_docs/README.md

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+# Flow Execution Examples
+
+This directory contains detailed execution examples demonstrating how Flow's capture mechanisms work with various driver and follower combinations. These examples are designed to help developers understand:
+
+- How data flows through the synchronization pipeline
+- When and why captures succeed, retry, or fail
+- Edge cases and potential pitfalls
+- Message dropping scenarios and how to avoid them
+
+## Document Index
+
+| Document | Description |
+|----------|-------------|
+| [Driver Examples](./drivers.md) | Detailed examples for all driver types (Next, Batch, Chunk, Throttled) |
+| [Follower Examples](./followers.md) | Detailed examples for all follower types |
+| [Combined Workflows](./combined_workflows.md) | Real-world scenarios combining drivers and followers |
+| [Edge Cases & Failures](./edge_cases_and_failures.md) | Common failure scenarios and how to handle them |
+| [Message Dropping Scenarios](./message_dropping.md) | When and why messages get dropped |
+| [Delay Configuration](./delay_configuration.md) | How delay parameter works, configuration options, and use cases |
+| [Boundary Calculation Reference](./boundary_calculation.md) | **Important:** Clarifies `lower_stamp` vs `upper_stamp` usage in followers (includes documentation discrepancy notes) |
+| [Before vs ClosestBefore](./before_vs_closest_before.md) | Detailed comparison with robotics use cases for choosing between these two followers |
+
+## Quick Reference: State Outcomes
+
+| State | Meaning | Action |
+|-------|---------|--------|
+| `PRIMED` | Capture successful | Process data |
+| `RETRY` | Need more data | Wait and try again |
+| `ABORT` | Cannot synchronize | Frame dropped, continue |
+| `TIMEOUT` | Wait expired (MT only) | Retry or handle timeout |
+| `ERROR_DRIVER_LOWER_BOUND_EXCEEDED` | Timestamp violation | Critical error |
+| `SKIP_FRAME_QUEUE_PRECONDITION` | Queue monitor rejected | Continue to next frame |
+
+## Visual Legend
+
+In the execution traces, we use the following notation:
+
+```
+Queue State:  [oldest] ← ← ← [newest]
+              [0, 1, 2, 3, 4, 5]
+                ↑
+              Elements ordered by timestamp
+
+Capture Range: {lower_stamp, upper_stamp}
+               {10, 15} means timestamps 10 to 15
+
+Timeline:
+    t=0   t=5   t=10   t=15   t=20
+    |-----|-----|------|------|
+
+    ▼ = captured element
+    ✗ = removed element  
+    ○ = retained element
+```
+
+## Common Patterns
+
+### Pattern 1: Frame-by-Frame Processing
+```cpp
+driver::Next + follower::ClosestBefore
+// Use when: Processing data one frame at a time with nearest-neighbor matching
+```
+
+### Pattern 2: Sliding Window Analysis
+```cpp
+driver::Batch + follower::Ranged
+// Use when: Need overlapping windows for moving average, etc.
+```
+
+### Pattern 3: Non-Overlapping Batch Processing
+```cpp
+driver::Chunk + follower::Before
+// Use when: Processing fixed-size batches without overlap
+```
+
+### Pattern 4: Rate-Limited Processing
+```cpp
+driver::Throttled + follower::Latched
+// Use when: Input rate higher than processing rate, need stable state
+```
+
+### Pattern 5: Optional Data Streams
+```cpp
+driver::Next + follower::AnyBefore
+// Use when: Some data streams may not always have data
+```