Expand Waterboy product presentation

[Chris-ObtuseAI]

What changed

• rebuilt the Waterboy landing experience as a complete product presentation
• added a live engine pulse, proof band, capability story, and explicit authority boundary
• documented the six-stage capture-to-publish pipeline and domain-neutral architecture
• added projection anatomy, seven league-specific cards, fidelity gates, replay governance, workflow, API surface, and evidence FAQ
• connected current-window counts and engine integrity to live API data
• added hero navigation into the current-week board and hypothetical Matchup Lab
• polished desktop, tablet, and 390px mobile layouts
• refreshed the tracked README showcase image and release evidence

Why

The working engine was already production-capable, but the landing page compressed
its architecture and differentiators into a short overview. This change makes the
product understandable and impressive without hiding its evidence boundaries or
overstating forecast calibration.

User impact

Visitors can now understand exactly how Waterboy captures data, estimates team
state, simulates score worlds, selects projected winners, communicates uncertainty,
isolates league semantics, and guarantees deterministic replay before using the
live board or Matchup Lab.

Validation

• Ruff: pass
• strict mypy: pass, 43 source files
• pytest: 74 passed
• JavaScript syntax: pass
• desktop browser: 1600x1000 and 1440x900
• mobile browser: 390x844
• browser console: zero errors and zero warnings
• hypothetical matchup flow: pass
• internal anchors: 12 checked, zero missing
• release evidence: 7/7 provisional anchors and 49/49 controls
• wheel build and presentation asset inspection: pass