docs(desktop): formalize launch target state

[Whiteks1]

Closes #411.

Summary

• Formalizes Launch as a first-class QuantLab Desktop workstation capability, not a separate product identity or trading-console protagonist.
• Defines research_ui as a continuity boundary for real-path smoke/runtime checks and browser-backed job/launch flows that are not yet native.
• Updates the product surfaces inventory so Artifacts are documented as integrated into Run Detail rather than restored as a separate protagonist tab.
• Adds an ADR clarification for the v0.1 legacy release surface vs future React migration direction.

Scope statement

#411 formalizes desktop product intent and continuity boundaries; it does not implement Launch expansion or legacy retirement.

Out of scope

• No UI code changes.
• No Launch surface implementation.
• No legacy renderer retirement.
• No research_ui removal.
• No Stepbit, Quant Pulse, or React renderer cleanup.

Validation

• git diff --check

Notes

• desktop(product): decide launch target-state and replace embedded continuity where required #358 and desktop(cleanup): retire legacy shell renderer after new Desktop migration slices land #356 were already closed before this slice; this PR documents the current target-state decision without reopening either issue.

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