feat: native transparent session filesystem preview

[jstar0]

Outcome

• Adds the transparent-session storage/runtime implementation, guarded enrollment, fork-family and archive lifecycle, physical storage budgets, recovery, and cross-platform service hosts.
• Adds the Apple-native Swift FSKit extension with versioned UDS IPC to the Go daemon, isolated mounted behavior tests, crash supervision, build identity, and atomic app/binary/definition rollback.
• Establishes contributor, maintainer, security, Issue/PR, CODEOWNERS, and CI standards for multi-person collaboration.
• Aligns the canonical contract and public status: native FSKit is the terminal macOS candidate; FUSE-T remains historical evidence and a development fallback only.

Safety boundary

• Production ~/.codex routing and production com.codexfold.fs remain disabled.
• No production rollout or state database was migrated by this branch.
• Native source deletion and bulk enrollment remain release-gated.

Verification

• go test ./...
• go test -race ./...
• go vet ./...
• git diff --check
• Linux amd64 CGO-disabled build
• Windows amd64 CGO-disabled build
• Linux and Windows test-binary cross-compile
• Xcode Release build for the Swift FSKit app and extension
• Isolated native FSKit mounted behavior and service crash/rollback gates recorded in the validation documents

Open product gates

• Install and benchmark the bounded native FSKit read-ahead candidate, including cross-handle and external-write coherency.
• Complete isolated real Codex CLI/Desktop resume, fork, archive, restart, and exact JSONL acceptance on the native route.
• Complete power-loss, retention, Linux real-client, and Windows real-host gates before any production-ready claim.

[jstar0]

This repository has been mirrored as the independent organization repository samekind/codexfold, and the equivalent review is now samekind/codexfold#1. Future development and review continue in the organization repository.