[codex] Add Principia cloud library

[pzqpzq]

Summary

Adds the Principia V1.1 Cloud Library foundation:

• deterministic gzip .pcz cloud packs, route indexes, search indexes, manifests, schemas, and validation workflows
• cloud resolver/hydration path integrated into research extraction to skip fresh cloud hits
• upload preparation with normal/newer/model-missing/force decision semantics and server-side admin-key checks
• Cloud Library dashboard at /cloud with stats, filtered search, contribution export, crawler planning, and admin operation export
• local CLI commands under python3 principia.py cloud ...

Large generated cloud packs remain out of git and are intended for GitHub Releases. The checked-in cloud/manifests/latest.json remains an empty pointer until release assets are published.

Validation

• python3 -m compileall -q principia tests
• python3 -m unittest tests.test_cloud_v1_1 -v
• python3 -m unittest discover -s tests -v
• PRINCIPIA_RUN_SCALE_TESTS=1 python3 -m unittest tests.test_cloud_v1_1.CloudV11Tests.test_100k_synthetic_snapshot_scale_is_opt_in -v
• local browser/API smoke test for http://127.0.0.1:8793/cloud

Notes

Direct release-asset publication is still separate because this environment does not have gh installed. The local seed release-style assets are generated under dist/cloud-seed/ and ignored by git.

[pzqpzq]

Release publishing note: after this PR is merged, run the principia-cloud-release workflow from GitHub Actions with a tag such as principia-cloud-seed-v1.1.0. The workflow now exports the snapshot from data/principia.sqlite, rewrites manifest asset URLs to GitHub Release download URLs, uploads the pack/index assets, and commits cloud/manifests/latest.json with the generated manifest pointer.