DFPY-71: Land v4.5 release-prep baseline

[sidmohan0]

Summary

• Rename the repo agent guide from Claude.md to AGENTS.md and add Linear/triage/domain agent context under docs/agents/.
• Align release-prep version context around stable 4.4.0, development 4.4.0a5, and target 4.5.0.
• Keep optional public exports lazy at package import time and retain the Donut/OCR lazy import crash fix.
• Derive the Sphinx release from datafog.__about__.__version__ instead of a stale hard-coded docs version.
• Make the click dependency explicit for fresh cli/nlp installs after CI exposed that newer typer no longer pulls it in transitively.

Validation

• .venv312/bin/python -m pre_commit run --all-files --show-diff-on-failure
• DATAFOG_INSTALL_PROFILE=cli DATAFOG_NO_TELEMETRY=1 DO_NOT_TRACK=1 .venv312/bin/python -m pytest tests/test_install_profiles.py -q
• DATAFOG_INSTALL_PROFILE=nlp DATAFOG_NO_TELEMETRY=1 DO_NOT_TRACK=1 .venv312/bin/python -m pytest tests/test_install_profiles.py -q
• DATAFOG_NO_TELEMETRY=1 DO_NOT_TRACK=1 .venv312/bin/python -m pytest tests/test_donut_lazy_import.py tests/test_no_network_core.py tests/test_runtime_dependency_safety.py tests/test_ocr_integration.py -q
• DATAFOG_NO_TELEMETRY=1 DO_NOT_TRACK=1 .venv312/bin/python -m pytest -m "not slow" -q
• .venv312/bin/ruff check .
• .venv312/bin/black --check .
• git diff --check

Refs DFPY-71