docs(simulation): replace overview lifecycle chart with hand-authored loop diagram

[khushalsonawat]

What

Replaces the Mermaid lifecycle chart on the Simulation overview (/docs/simulation) with a hand-authored SVG, agent-development-loop.svg, in the same visual style as replay-loop.svg.

Why

The lifecycle has two loops (Score → Fix → Simulate, and Observe → Replay → Simulate), and Mermaid's layered layout can only render those as long back edges hooking around the whole canvas, which made the diagram clumsy and confusing.

How

• Simulate, Score, Deploy, Observe at the cardinal points of one circle, four equal-radius arcs clockwise (the ship loop)
• Fix at the centre with straight chords Score → Fix → Simulate, so the iterate loop cuts through the middle instead of routing around the outside
• Build feeds in from above as the entry point; the Observe → Simulate arc carries the Replay label
• Stroke width 1.2, standard block style, kebab-case SVG attributes

Recording

View at /docs/simulation on a local dev server, or open public/images/docs/simulation/agent-development-loop.svg directly.

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