chore: update README.md

[MichaelsEngineering]

What

• Updates README.md to remove the repeated "overnight" claim from the repository overview and project goal.
• Keeps the repo description focused on bounded paper drafts, literature summaries, and model proposals without implying a specific turnaround time.

Why

• Aligns the public-facing project description with the current workflow claims and avoids overstating delivery timing.
• Reduces ambiguity in the README by describing the research process more generally.

How

• Edited the introductory README prose in two places and left the rest of the document unchanged.
• Verified the branch contains a single README-only commit (35ab07d chore: update README.md).
• Ran make check locally.

Checks

• make check passes locally
• Added/updated tests
• Docs or README updated if needed
• Security impact assessed (none or brief rationale provided below)
• Dependency and lockfile changes explicitly listed
• Supply-chain provenance updated (SBOM/attestation artifacts linked when applicable)
• Threat-model delta captured for behavior/config changes
• Rollback plan included for this change
• Confirmed no new network/time/nondeterministic sources in core loop paths (src/runner.py, src/replay.py, src/replay_fixtures.py)

Security Notes

• Security impact: none; this change only updates README wording and does not modify runtime behavior.
• Dependency or lockfile changes: none.
• Threat-model delta: none; no code, config, or interface changes.
• Rollback plan: revert commit 35ab07d to restore the prior README wording.