docs: clarify what runs today

[yihanzhu]

Why

README mixed the live in-session profile, the landed manual v2 foundation, the paused event-driven lane, and the portable target architecture. The landing page also incorrectly said yshifu merges.

What changed

• Add a short current-status section to README.
• Clarify that the current loop uses a GitHub issue spec, not a v2 work artifact.
• Replace the old Phase 1 / Phase 2 README wording with today / next.
• Change the two landing-page merge labels so the operator is the merger.

Deliberately deferred

The thorough repo-wide documentation and prompt cleanup belongs to work/plain-language-cleanup/intent.md. This PR does not change quickstart, restore, work docs, prompts, templates, scripts, workflows, policy, or CI.

Proof

Run on commit b22e4a8f62845405db5e64c742d9ddbe700ad174:

• Only README.md and website/index.html differ from main.
• git diff HEAD^ --check passed.
• scripts/check-rename.sh passed.
• The landing-page merge heading and no-agent-merge text render locally with no console errors.
• No shell or runtime file changed; CI supplies the repository-wide gate.

Closes #176

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[yihanzhu]

Closing at the operator's request. The documentation work will be handled through work/plain-language-cleanup/intent.md. Nothing in this PR was merged or accepted as the later cleanup.