Lifts the async web fetcher into aborist as an opt-in source. The
implementation comes directly from ~/git/agents.ai.unturf.com/core
(rev 2026-04-28); aborist's adaptations are minimal and documented in
aborist/sources/crawler/__init__.py:
core/async_web_fetcher.py -> aborist/sources/crawler/async_web_fetcher.py
core/web_fetch.py -> aborist/sources/crawler/web_fetch.py
Two source-side changes during the lift:
1. Heavy deps (aiohttp, bs4, miniuri) wrapped in try/except so a bare
`import aborist.sources.crawler` raises ImportError with the install
hint instead of leaking AttributeErrors deep in user code.
2. Chat-bot fetch triggers (`has_fresh_fetch_trigger`,
`has_web_fetch_trigger` from agents.ai.unturf.com/core/keywords)
replaced with NotImplementedError stubs. Aborist has no chat
surface — fetch intent is detected at the application layer. The
two test classes that exercised these triggers are
`@pytest.mark.skip`'d with the same rationale.
Not lifted: web_cache_manager.py — it backs page caching with
SQLAlchemy. Aborist has its own content-addressed cache via
providence_cache; no need to carry SQLAlchemy as a dep just for
crawled-page memoization.
Off by default:
- `[crawler]` extras section in pyproject.toml carries the heavy
deps. `[dev]` pulls them in so the crawler tests can run.
- `make test` ignores tests/crawler/ entirely.
- `make bootstrap-crawler` installs the extras into the venv.
- `make test-crawler` runs only the lifted tests after extras land.
Tests: 74 passed, 9 skipped (the chat-bot trigger tests deliberately
dropped). Default `make test` stays at 273 passed, 1 skipped.