Add coreanalyzer experiment routing generate through the analysis core

[kyleconroy]

Summary

SQLCEXPERIMENT=coreanalyzer routes sqlc generate through the core catalog and analyzer — the same path sqlc analyze and the ClickHouse and GoogleSQL engines already use — instead of each engine's own analysis path.

• New experiment in internal/opts: coreanalyzer (no prefix to disable, case-insensitive). When set, parse() builds each query set's compiler with compiler.WithCoreAnalysis().
• Experiment wiring: Env.Experiment was parsed from the environment but never reached the compiler — processQuerySets always built empty parser options. It now threads the experiment through.
• Codegen through the core: a core-mode Result carried a nil catalog, which pluginCatalog would dereference — generate had never run on this path (ClickHouse/GoogleSQL only have parse/analyze cases). catalog_core.go now dumps the core catalog into the legacy catalog shape after the schema is applied, so codegen builds models as usual. Seeded pg_catalog/information_schema relations come along but codegen already skips those schemas.
• Array fix: codegen renders one [] per ArrayDims, which the core path never set — array columns silently generated as scalars (Tags string instead of Tags []string, no pq.Array scan). Both the catalog dump and core query columns now set ArrayDims: 1 when the core reports an array.

Output through the core matches the legacy path exactly for the covered cases, except SELECT * / RETURNING * stay literal in the emitted SQL: the core takes columns from analysis rather than rewriting the query text.

Also documents the experiment in docs/reference/environment-variables.md, replacing the stale "no experiments are defined" note.

Rebased on main after #4545 removed the analyzerv2 experiment; coreanalyzer is now the only experiment, so the wiring passes Env.Experiment through unscoped.

Testing

• New end-to-end case internal/endtoend/testdata/experiment_coreanalyzer/ with committed goldens for postgresql (stdlib), sqlite, and mysql, run via exec.json env SQLCEXPERIMENT=coreanalyzer.
• Experiment parsing cases added to the existing internal/opts tests.
• Full suite green before the rebase: go test --tags=examples -timeout 20m ./... with PostgreSQL and MySQL live. After the rebase: go build ./..., the opts/compiler package tests, and the three experiment_coreanalyzer replay cases.

🤖 Generated with Claude Code

https://claude.ai/code/session_01ANVHEs41RJbybS3ja9N1SA