Rebuild docs OKF and LLM Wiki

[yvette-carlisle]

Summary

• Rebuild docs/ into the Decodex OKF lane shape: spec, runbook, reference, decisions, research, and evidence.
• Remove the legacy top-level docs/guide and docs/plans lanes; move runbooks, evidence, retained plan artifacts, and fixture JSON to their owning locations.
• Promote settled research into decisions/evidence and preserve unresolved valuable points as active research contracts.
• Update README, Makefile tasks, scripts, Rust report generation, and tests for the new paths.

Validation

• git diff --check
• cargo make check-docs
• decodex docs check
• cargo make fmt-check
• JSON parse check for moved fixtures and report snapshots
• cargo make check-rust
• cargo test -p elf-eval --test real_world_job_benchmark -- --test-threads=1
• cargo make lint
• cargo make test-rust