ci: SQL E2E over subprocess + http + unix transports

[rustyconover]

Adds multi-transport VGI coverage to the SQL E2E suite: the same test/sql/*.test suite now runs over subprocess, http, and unix transports in real CI (3 transports x 2 OS = 6 integration legs).

What changed

• ci/run-integration.sh parameterized by a TRANSPORT env var (default subprocess):
  • The canned-response mock news server (importlib-loaded _Handler from scripts/run_sql_e2e.py) stays up for all transports; its VGI_NEWS_*_BASE_URL / VGI_NEWS_TIMEOUT vars are exported, so an out-of-band-booted (http/unix) worker inherits them.
  • http: injects INSTALL httpfs FROM core; LOAD httpfs; into staged tests (the vgi HTTP transport rides DuckDB's httpfs), boots news_worker.py --http --port 0 --port-file <f>, polls the port-file, and ATTACHes http://127.0.0.1:<port>.
  • unix: boots news_worker.py --unix <sock>, polls for the socket, ATTACHes unix://<sock>.
  • One cleanup() trap captures $? first and kills both the mock and the worker.
  • Silent-skip guard (tee + PIPESTATUS): the runner auto-SKIPs any error containing "HTTP" (a green-looking fake pass), so the leg fails unless All tests passed (N>0 assertions) and zero skips.
• pyproject.toml + news_worker.py PEP 723 header gain an http extra (vgi-python[http], waitress); uv.lock relocked.
• .github/workflows/ci.yml: integration job is now a transport: [subprocess, http, unix] x os matrix, installing with uv sync --frozen --extra http. The test and lint jobs are unchanged.
• ci/README.md rewritten for news (transport matrix, discovery, httpfs-on-http, silent-skip guard, externalized cursor).

Streaming over HTTP

news_search is a paging table function, but its cursor is already externalized into the serializable NewsScanState (plain ints/bools/strings; no fetched rows carried in state — each process() tick re-fetches deterministically from the cursor). So it resumes correctly over the stateless HTTP transport across the batch boundary. The http leg runs the full suite including news_scan_state.test (the GDELT window cursor hops to the second window and emits "Older C", reachable only via the resumed cursor) — nothing gated, no worker change needed.

Local validation (all GREEN)

• subprocess: 39 assertions
• unix: 39 assertions
• http: 45 assertions (39 + injected httpfs INSTALL/LOAD across 3 files)

🤖 Generated with Claude Code