init: seed Ratatoskr from corviduo-project-template + ship v0 scaffold

Worldtree Conversation API debug TUI. Multi-pane observability dashboard:
chat transcript + persona/Vili affect log + tool events + admin events +
Bifrost state + tool inventory + (opt-in) raw server log.

Design locked at docs/design-brief.md (originated as
brokkr-smithy/docs/ratatoskr-design-brief.md). Operator-locked decisions:

- Textual application-shell framework (multi-pane dashboard, not REPL).
- Separate repo + separate dev team (no Worldtree-source imports).
- httpx-sse for SSE consumption (reference Python SSE-resume impl).
- Triple version-skew mitigation: spec-pin in pyproject.toml + recorded
  SSE snapshot tests + conformance smoke. Initial pin: Worldtree v0.19.0
  at 55101e909abcd2219833266b6f905c5bc956e0f0.
- Persona pane: label-don't-refuse PII posture.
- Server-log pane: opt-in via --server-log <path>.
- Two-stage Ctrl-C (cancel then exit).
- Markdown rendering default-on; --raw opt-out.

In the box:

- docs/design-brief.md — the locked design with full rationale.
- docs/SPEC-PIN.md — Worldtree spec pin + bump procedure.
- docs/conversation-api-spec.md + docs/conversation_api.contract.md —
  vendored Worldtree spec snapshots at the pinned SHA.
- pyproject.toml — Python 3.12, hatchling, uv-managed, deps locked.
- src/ratatoskr/ — stub package (cli.py raises NotImplementedError).
- tests/test_no_worldtree_imports.py — boundary smoke test PASSING.
- tests/snapshots/README.md — recording convention for SSE snapshot tests.

Not in the box yet:

- Gitea remote (operator/infra-ops to register at vh/ratatoskr).
- Implementation — the dev team owns this; design brief is the spec.

Origin: althing thread 01KS3R34XD3N6HMK91VXESHGW7 (worldtree-dev →
brokkr-smithy-dev, 2026-05-20). Volva consulted via thread
01KS3VF6W33N3V5FNMGQ91YNVD.

.gitignore

@@ -0,0 +1,114 @@
+# Local environment variables (contains secrets)
+env.sh
+
+# Sleipnir per-project config (per-checkout overrides; user-global lives at ~/.config/sleipnir/)
+.sleipnir/config.yaml
+
+# Workspace data
+data/
+
+# Logs
+logs/
+
+# ---> Python
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
+
+# Ruff
+.ruff_cache/
+
+# uv / pdm / poetry caches
+.pdm-python
+__pypackages__/
+
+# IDEs
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db