[evanlowe]

Accept PostgreSQL hosts such as db.example.test:6543 without appending the separately configured port a second time. The embedded port takes precedence; a plain hostname continues to use DATABASE_POSTGRESQL_PORT (default 5432). Reject empty hostnames and embedded ports that are not ASCII decimal integers in 1..65535, before creating the session service.

The change is limited to the PostgreSQL backend and 26 regression cases. Both driver branches share the parsing, and explicit db_url handling is unchanged. Only single-colon endpoints receive the new handling; this does not add IPv6 parsing.

Validation on 2026-10-28, diff at 5647ed15:

• pass: uv run --extra dev pytest tests/memory/test_postgres_endpoint.py tests/memory/test_postgres_schema.py tests/test_adk_compat.py -q --tb=short — 47 passed. The new regression cases were also exercised before the fix and reproduced the duplicate-port failure.
• pass: uv run --extra dev pre-commit run --all-files — Ruff, formatting, secret scans, and dependency policy.
• blocked by local optional dependencies: the broader two-worker regression run had 7,787 passed, 16 failed and 2 collection errors involving missing llama_index, openai_codex, and anthropic. A subsequent retry of those modules plus the affected tests had 173 passed and 2 collection errors for anthropic. CI remains the full-suite gate; no live database was used.