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 through #4543 (extension catalog seed files). #4545 removed the analyzerv2 experiment, so coreanalyzer is now the only one and 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.
• go test ./... green on the rebased branch with PostgreSQL and MySQL live, including the full endtoend package and the three experiment_coreanalyzer replay cases.

🤖 Generated with Claude Code

https://claude.ai/code/session_01ANVHEs41RJbybS3ja9N1SA

[kyleconroy]

The buf / build failure on 96b5207 is a transient rate limit, not something in this diff. It failed during setup, before any buf command ran:

Setting up buf version "1.50.0"
Resolving the download URL for the current platform...
##[error]API rate limit exceeded for 172.183.131.23.

bufbuild/buf-setup-action@v1 resolves the buf release URL through the GitHub API, and .github/workflows/buf.yml passes it no token, so the request is unauthenticated and subject to per-IP limiting on shared runners — the job logs the action's own warning, No github_token supplied, API requests will be subject to stricter rate limiting. This diff touches no .proto or buf files at all, and run 2271 is the only buf failure in the last ten runs; run 2268, on this same branch, passed.

It needs a re-run, which I can't trigger — the app token here has no actions: write. The durable fix would be adding github_token: ${{ github.token }} to the buf-setup step, but that's an unrelated CI change I'd rather not land inside this PR. Happy to send it separately if you want it.

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