[zuudevs]

Summary

Adds docs/roadmap.md as the implementation-order source of truth for the frozen cpp_request v1 requirements.

Roadmap structure

• v0.1 — requirements, architecture, API/error contracts — complete
• v0.2 — URL/native sockets/DNS/TCP transport — complete
• v0.3 — request model and serialization — complete
• v0.4 — response parser and body framing — complete
• v0.5 — public Client core — in progress via PR feat: add public Client core execution path #15
• v0.6 — connection reuse / keep-alive
• v0.7 — redirect handling
• v0.8 — protocol/API correctness hardening
• v0.9 — packaging, benchmarks, examples, documentation
• v1.0 — release hardening and acceptance gate

Captured gaps

The roadmap explicitly records remaining frozen-requirement work that was easy to overlook while implementing feature PRs, including:

• query parameter / percent-encoding contract
• connection reuse
• redirects
• Result<T> hardening
• installable CMake package/export
• required benchmark targets
• user-facing examples and README
• thread-safety documentation
• cross-platform/release acceptance checks

Scope control

The document also restates the frozen v1 exclusions and defines a roadmap-maintenance rule so future scope/order changes are reflected explicitly.

This PR is documentation-only and is intentionally separate from the open Client core PR.