P1: DB-level RLS backstop (non-owner role, FORCE RLS, per-request scope)

[gnanirahulnutakki]

Phase 1 — the DB-level backstop. Implement PostgreSQL RLS that is actually enforced, independent of application code (the predecessor advertised RLS but it was inert).

Tasks

• App connects as a non-owner DB role
• ENABLE and FORCE ROW LEVEL SECURITY on every workspace-scoped table
• Set current workspace per request inside the transaction (set_config('sith.workspace_id', …, true)); policies check it
• CI guard forbidding un-scoped access to workspace-scoped tables

Acceptance

• A deliberately app-layer-bypassed cross-workspace query is denied at the DB layer.

Refs: ADR-0003.

[gnanirahulnutakki]

Delivered by PR #77 and merged to dev as 122a5f2. Local full CI, real PostgreSQL 18.4 RLS falsification, and real two-cluster kind regression passed. PR CI run 29177223200 and post-merge dev CI run 29177407504 both completed successfully, including the new forced-RLS container test, vulnerability scan, race tests, reproducible archives, SPDX SBOM, and kind. Codex Security MCP remained intentionally skipped per operator direction. Follow-on #12 owns the unified destructive isolation suite and removed-policy negative control.