0.76.1

## Clearer Scenario Graph Rendering

This is a rendering-only fix for the scenario graph introduced in 0.76.0 — nothing changes in how scenarios actually run.

When a scenario had reusable calls, its dependents were drawn branching off in parallel with the calls, which didn't match the actual execution order (dependents run after the calls complete). The graph now draws the dependency edge from the last reusable call node, so the drawing matches what already happens at runtime:

Before:

```mermaid
graph LR
  classDef reusable fill:#e8f0fe,stroke:#4285f4
  n0["login-flow"]
  n1["premium-content<br/>Play premium content"]
  n2[["login (user=paid)"]]:::reusable
  n0 -.-> n2
  n0 --> n1
```

After:

```mermaid
graph LR
  classDef reusable fill:#e8f0fe,stroke:#4285f4
  n0["login-flow"]
  n1["premium-content<br/>Play premium content"]
  n2[["login (user=paid)"]]:::reusable
  n0 -.-> n2
  n2 --> n1
```

Dashed edges are reusable calls made by the scenario; solid edges are dependents. This applies to both `arbigent graph` (Mermaid output) and the scenario graph dialog in the UI.

## What's Changed
* Start dependency edges from the dependency's last call node in scenario graph by @takahirom in https://github.com/takahirom/arbigent/pull/396

**Full Changelog**: https://github.com/takahirom/arbigent/compare/0.76.0...0.76.1