design: adopt gluesql-core as the SQL engine, drop bundled SQLite (DD-069, REQ-231)

[avrabe]

Records the verified outcome of the SQL-engine research + prototype (you chose "swap, verify-first").

Verdict: GO — migrate to gluesql-core

Prototype (proto/gluesql-verify, throwaway) confirmed:

• Dialect ✓ — the V-closure JOIN with NOT IN (subquery) and UPDATE artifacts SET … WHERE … both execute in gluesql's dialect (the core risk, retired).
• Weight ✓ — but only via gluesql-core. The umbrella gluesql crate pulls every storage backend (csv/parquet/sled/redb/mongo/redis/git) and compiles cc (~55s). gluesql-core + memory-storage compiles only sqlparser + core (pure Rust, no cc, ~19s). rusqlite bundled compiles the SQLite-C amalgamation per job — the CI weight that made feat(sql): rivet sql write slice — UPDATE via validate + safe YAML edit (REQ-230) #582 sit ~40 min queued (CI: self-hosted runner disk exhaustion fails all compile gates; post-job cleanup hook frees nothing #567).
• Async — Glue::execute is async; bridge into the sync sql::query/plan_write via a small block_on.
• Architecture bonus — gluesql-core's Store/StoreMut traits let rivet's store be the DB (DD-068's virtual-tables vision): reads + writes go native, deleting the read-path copy and the write-path staging-diff.

What this PR is

Design artifacts only (DD-069 + REQ-231). The migration itself (REQ-231) is the focused follow-up: swap the engine behind the unchanged sql::query/plan_write API, remove rusqlite + libsqlite3-sys, keep all read/write/serve tests green.

🤖 Generated with Claude Code

[github-actions]

📐 Rivet artifact delta

Change	Count
Added	2
Removed	0
Modified	0
Downstream impacted (depth ≤ 5)	0

Graph

graph LR
  DD_069["DD-069"]:::added
  REQ_231["REQ-231"]:::added
  classDef added fill:#d4edda,stroke:#28a745,color:#155724
  classDef removed fill:#f8d7da,stroke:#dc3545,color:#721c24
  classDef modified fill:#fff3cd,stroke:#ffc107,color:#856404
  classDef overflow fill:#e2e3e5,stroke:#6c757d,color:#495057,stroke-dasharray: 3 3

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Added

• DD-069
• REQ-231

📎 Full HTML dashboard attached as workflow artifact rivet-delta-pr-585 — download from the workflow run.

_{Posted by rivet-delta workflow. The graph shows only changed artifacts; open the HTML dashboard (above) for full context.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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