Restructure docs for Bridgetown migration; add AGENTS runbook and reference docs

[blackopsrepl]

Motivation

• Consolidate repository documentation into docs/ and prepare for a Bridgetown-based website migration.
• Establish a clear reference/ layout and keep implementation runbooks in bridgetown/ to make migration deterministic.
• Provide agent-scoped guidance for automated edits and migration tasks via AGENTS.md and runbooks.

Description

• Update README.md to point to new docs/reference/... paths and to reference docs/README.md as the docs entrypoint.
• Add docs/AGENTS.md with scoped instructions for agents and a validation checklist.
• Add docs/README.md and docs/bridgetown/{agent-runbook.md,execution-plan.md} to document the Bridgetown migration workflow and exact local run steps.
• Move existing top-level docs into docs/reference/ and add docs/reference/github-pages-migration.md describing GitHub Pages migration options.

Testing

• No automated tests were executed because this is a documentation-only change.

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Codex Task

[chatgpt-codex-connector]

💡 Codex Review

solverforge/docs/reference/typed-contract-audit.md

Line 1 in f4ccac8

# Typed Contract Audit and Unification Plan

Preserve old typed-contract-audit path or update all refs

Moving this document to docs/reference/typed-contract-audit.md without a compatibility stub leaves existing in-repo references broken; for example, crates/solverforge-core/WIREFRAME.md:612 still points to docs/typed-contract-audit.md, which now resolves to a missing file. This creates immediate doc navigation regressions for readers following the wireframe, so the move should be paired with either reference updates in the same commit or a redirect/stub at the previous path.

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