docs: align public product language with current Valtide semantics

[chin0312]

Summary

• Align the landing page, role-based documentation, and methodology page around Observed xStock, Valtide Fair Value, Valuation Range, Underlying Anchor, X-Perp, Evidence State, and Policy Action.
• Explain that Observed xStock is also an input to the Valtide Model, so their difference is not independent market evidence; keep X-Perp separate and the Underlying Anchor contextual.
• Scope the 11,828 / 94.3% / 19% figures to the exposed NVDAx P1a-C v0.2.0 June–September 2026 interval study. State that this is development/historical evidence, not raw-xStock accuracy, three-asset results, Evidence State accuracy, production performance, or an untouched test.
• Clarify that the browser is read-only while the backend scheduler publishes authorized attestations for configured assets; X Layer records evidence and evaluates policy rather than calculating Fair Value.
• Use the shared reasonLabel() formatter in the landing demo and preserve role-specific technical details for researchers/developers.

Scope

Copy and regression tests only. No CSS, API/backend behavior, quant artifacts, Evidence State logic, contracts, or deployment changes. Current production scope remains NVDAx, SPYx, and AAPLx; QQQx remains research-only.

Verification

• cd apps/web && npm test — 60 passed
• cd apps/web && npm run build — passed (existing Vite large-chunk advisory only)
• git diff --check origin/main..HEAD — passed

No merge performed.

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Project	Deployment	Actions	Updated
valtide	Ready	Preview	Oct 7, 2026 4:20am UTC