Switch core catalog to ncruces/go-sqlite3 - #4542

Summary

The analysis core was the last user of modernc.org/sqlite; every other SQLite path (vet, the sqlite engine analyzer, sqlite3ext, sqltest) already uses ncruces/go-sqlite3, which as of v0.35 is wasm2go-generated pure Go with no wazero runtime. Switching the core catalog over leaves a single SQLite implementation in the binary and drops the entire modernc dependency tree (9 go.mod lines, 45 go.sum lines).

• internal/core/catalog.go: driver import and name (sqlite → sqlite3); both DSN forms (:memory: and file:...?mode=ro&immutable=1) carry over unchanged.
• internal/core/cache.go: catalog serialization goes through the driver's Raw() escape hatch and ext/serdes instead of modernc's Serialize method.

Foreign keys

ncruces compiles SQLite with SQLITE_DEFAULT_FOREIGN_KEYS=1, unlike stock SQLite and modernc. Silent enforcement broke MySQL dialect seeding: UNHEX in internal/engine/dolphin/dialect/functions.jsonl declares "returns": "", leaving a dangling sql_proc.return_type_oid that modernc never checked. The catalog now pins PRAGMA foreign_keys = OFF explicitly, preserving the previous semantics where the schema's foreign keys are documentation. The dangling seed record itself is left for a follow-up, along with an FK-enabled audit of the other dialect seeds.

Benchmarks

internal/core/analyzer benchmarks, n=10, benchstat, linux/amd64 (Xeon 2.10GHz):

Allocations drop ~3.4%; CPU time is up across the board. The trade is single-digit analysis overhead for one SQLite implementation instead of two. The catalog cache absorbs the CatalogNew/ApplySchema cost on warm runs, so the steady-state cost is the Prepare delta.

Testing

• Full suite green with live PostgreSQL and MySQL: go test -timeout 20m ./...
• Serialize → cache → immutable-reopen roundtrip verified during development

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https://claude.ai/code/session_01J3BkQjNzN54dXhs3M1ypGr

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