Adopt src layout: move falcon/ to src/falcon/

[cweniger]

Summary

Converts the repo from a flat package layout to a src layout (falcon/ → src/falcon/). With the package under src/, a repo checkout no longer puts an importable falcon/ on sys.path, so imports always resolve to the installed package rather than being silently shadowed by the current working directory — the standard motivation for src layout, and a real footgun here since there are multiple local checkouts.

Changes

• git mv falcon src/falcon (30 files, pure renames — no content changes).
• pyproject.toml: setuptools package discovery gains where = ["src"].
• mkdocs.yml: mkdocstrings Python handler paths: [.] → paths: [src] so griffe finds the source.
• .github/workflows/docs.yml: docs path trigger falcon/** → src/falcon/**.

Unchanged / compatibility

• Import path (import falcon), the falcon console script (falcon.cli:main), and the falcon-sbi distribution name are all unchanged.
• tests.yml already runs pip install -e . before pytest --cov=falcon (import name, not path) — no change needed.
• publish.yml builds via python -m build, driven by the updated pyproject discovery.
• Verified discovery: find_packages(where="src", include=["falcon*"]) returns the same 5 packages (falcon, falcon.core, falcon.embeddings, falcon.estimators, falcon.priors).

After merging

Re-run pip install -e . in any working checkout so the editable install repoints at src/falcon. Note that with src layout, local pytest runs against the installed package, so the editable reinstall is required to test local changes.

Test plan

• find_packages(where="src", ...) discovers all packages
• No leftover top-level falcon/
• CI: pip install -e . + pytest -m "not slow" green
• CI: docs build (mkdocs) resolves API pages via paths: [src]

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 10.33%. Comparing base (90bccbf) to head (d081038).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #110   +/-   ##
=======================================
  Coverage   10.33%   10.33%           
=======================================
  Files          30       30           
  Lines        3927     3927           
=======================================
  Hits          406      406           
  Misses       3521     3521           

Flag	Coverage Δ
unit	10.33% <ø> (ø)

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