ci(pg19): bump pgvector to v0.8.3 + Windows event-loop policy (cherry-pick from fix/pg19-compat-and-demo)

[devopam]

Summary

Cherry-picks the two valuable PG 19 compat fixes from your fix/pg19-compat-and-demo branch (which was based on an older main predating the Phase 3 PRs and would have wiped out ~1,800 lines if merged directly). Both fixes are rebased onto current main.

What's in

1. pgvector v0.8.0 → v0.8.3 in .github/ci-postgres-pg19.Dockerfile

This is the proper fix for the pgvector PG 19 compile issue I worked around in PR #152 with a best-effort try-and-continue. v0.8.3 carries upstream PG 19 support (LWLock API rename handled). Now the expected path is "build succeeds and vector tests run on the PG 19 matrix entry."

PR #152's safety-net wrapper stays so a future PG 20 / upstream-lag scenario doesn't gate the rest of the image — but the warning text is updated to reflect v0.8.3 being the new pin.

2. Windows event-loop policy in scripts/smoke_test_pg19.py

Adds:

if sys.platform == "win32":
    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

Windows shells default to ProactorEventLoop which psycopg's async subsystem doesn't play well with. Selector loop runs cleanly. No-op on Linux / macOS.

What's intentionally left out

File	Why skipped
scratch/fetch_pgvector.py	Hardcoded c:\Users\devop\OneDrive\… path — personal local scratch
tests/unit/test_demo.py	Imports from a demo module that doesn't exist on either branch — broken on land

Roadmap impact

Closes the practical concern behind roadmap row 14.1's pgvector-on-PG-19 follow-up. Once this merges + main rebuilds, vector tests should run on the PG 19 matrix entry instead of skipping.

After this lands you can safely delete the source branch fix/pg19-compat-and-demo.

Test plan

• uv run ruff check scripts/smoke_test_pg19.py — clean
• Next CI run: Tests (PG 19) job's image build step succeeds with v0.8.3
• Vector-dependent integration tests no longer skip under PG 19

🤖 Generated with Claude Code

https://claude.ai/code/session_0122yLZLJ8t4W43sdN6BmTZc

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[gemini-code-assist-2]

Code Review

This pull request updates the PG 19 CI Dockerfile to pin and build pgvector v0.8.3, which is compatible with PostgreSQL 19, while keeping the try-and-continue safety net. Additionally, it configures the WindowsSelectorEventLoopPolicy in the smoke test script when running on Windows to prevent connection errors with the psycopg async subsystem. I have no further feedback to provide as there are no review comments to evaluate.