Update wiki and harden evidence ledger persistence

[Tashima-Tarsh]

Summary

• update docs/wiki to reflect the current DISHA v6.6 Constitutional Evidence OS product doctrine
• add wiki pages for architecture control plane, production spine, agentic AI roadmap, monetization/GTM, and the book thesis
• convert the evidence ledger to async storage architecture
• add Postgres-backed evidence event persistence when DATABASE_URL is configured, with in-memory fallback for local/open-source mode
• update mission, agentic, source-probe, and evidence-export flows to await evidence persistence
• update production spine metadata to mark evidence persistence as working, with mission persistence still listed as next hardening

Verification

• npm.cmd run verify

GitHub wiki note

Attempted to clone https://github.com/Tashima-Tarsh/Disha.wiki.git, but GitHub returned Repository not found. That means the GitHub wiki remote is not enabled or not accessible from this token. The versioned wiki source is updated under docs/wiki in this PR.