Slate v2 doc stack should separate live replacement truth from historical phase docs

Problem

The docs/slate-v2 stack grew by accretion.

That left too many docs trying to do the same job:

• front-door overview
• roadmap ownership
• architectural synthesis
• phase history
• release verdict

The result was not missing documentation. It was competing documentation.

Solution

Split the stack into two explicit classes:

1. Live replacement-truth docs
   • release readiness
   • family ledger
   • blocker list
   • evidence scoreboard
   • replacement-candidate guide in the repo
2. Historical / reference docs
   • engine north star
   • synthesis
   • cohesive program plan
   • frozen package roadmap
   • old phase artifacts

Then make the front-door overview point to the live set first and label the historical docs as reference-only.

Why This Works

The hard part was not writing more summary prose.

The hard part was deciding which docs are allowed to own the current truth.

Once the canonical set is small and explicit, the rest of the stack can stay useful without pretending to be the front door.

Reusable Rule

For large architecture / migration doc stacks:

• keep one small canonical live set for the current verdict
• label older phase, roadmap, and synthesis docs as historical/reference
• never let historical execution logs compete with the current replacement claim