release: close v1 manual acceptance review

[zuudevs]

Summary

Closes the deliberate manual acceptance phase after PR #30 made all automated v1 release gates green.

Manual review record

Adds docs/release/v1.0-manual-review.md covering:

• HTTP framing and connection-reuse review
• performance-claim discipline against the committed benchmark suite
• public API/lifetime contract review
• exported dependency/package boundary
• frozen-scope compliance
• version/tag/release metadata plan

The review found no code/API feature blocker before promotion.

Release notes draft

Adds docs/release/v1.0-notes.md as the draft user-facing v1.0 release notes.

Acceptance + roadmap status

• marks automated release gates passed
• records manual acceptance as passed on 2026-09-16
• moves the roadmap to v1.0 promotion pending
• keeps the project version at 0.9.0 intentionally

Manifest metadata fix

Synchronizes vcpkg.json from stale 0.1.0 metadata to the current 0.9.0 development version and updates the old project description.

Next step

After this PR is merged, the next change should be a focused 0.9.0 -> 1.0.0 promotion PR that updates both CMake and manifest versions, freezes remaining editorial pre-release API wording, finalizes release notes, and reruns all release gates.

No tag or GitHub Release should be created by this PR.