[codex] Align client snippet proof wording

[Atomics-hub]

What changed

• Updated the Claude/Codex/Cursor release-ticket detail to name packaged Claude MCP JSON and the Codex/Cursor command file.
• Updated the release-status evidence marker for the stronger wording.
• Updated v0.2 alpha release notes to say the objective checks the actual Claude MCP JSON and Codex/Cursor command file.

Why

PR #288 strengthened the objective to validate the real snippet files. The machine-readable release ticket, release-status marker, and release notes now describe the same contract.

Validation

• cargo fmt --check
• cargo run --locked -- release-status --json | jq '{ready_for_alpha_rc, offline_ticket: (.verification_gates[] | select(.name=="offline release ticket bundle"))}'
• cargo run --locked -- release-ticket --out dist/release-ticket-client-detail-proof --force --json | jq '{ready, client: (.checks[] | select(.name=="objective: Claude/Codex/Cursor sidecar"))}'
• cargo clippy --all-targets --all-features -- -D warnings
• cargo run --locked -- release-audit