feat(dag-viewer): plan SQL queries over declared tables in the editor

[zzylol]

Stack: #574 → #620 → #618 → #621 → #627 → #625 → #628 → #632 → #634 → #616 → #617 → #622 → #624 → #629 → #630 → #631 → #633 → #635 → #636 → #637

Problem

The query editor and stage_pipeline only planned PromQL; SQL needed a catalog, and the only SQL workload was Example 2's hard-wired flows table (Q54).

Changes

• stage_pipeline: repeatable --sql <query> and --table '<json>' ({"name", "columns": [{"name", "type": timestamp|utf8|string|float64|double|int64|bigint, "nullable" (default true)}], "time_index"?}; same semantics as dag_export's --table-schema, no default tables). A run is one language: mixing --promql and --sql is an error, as is --table without --sql; malformed tables, duplicate names and out-of-range time_index are errors, not panics. --epsilon/--delta/--interval-ms apply as for PromQL. Example 2's flows now goes through the same catalog code (its fixture output is unchanged). Header comment and USAGE updated.
• server.py: plan_args accepts language (promql|sql) and tables; validates 1–20 queries, ≤50 tables, 1–500 columns, non-empty and unique names, known types, time_index; passes --table <json>/--sql.
• Editor: PromQL/SQL switch (each language keeps its own draft), a "tables (JSON, one table per line)" box prefilled with flows, example query SELECT COUNT(DISTINCT src_ip) FROM flows; existing CSS tokens.
• The test helper's temp file name no longer embeds the arguments (a --table JSON made it too long).
• README editor section updated.

Test plan

• cargo fmt --check, cargo clippy --workspace --all-targets -- -D warnings
• cargo test -p asap-devtools: 47 passed (new: SQL over a --table writes a valid document with language "sql"; mixing languages, --table without --sql, bad table JSON, duplicate tables and undeclared tables error)
• cargo test --workspace: 1673 passed, 0 failed, 21 ignored (re-run after the rebase on main d4869a7)
• Viewer tests (python3 -m unittest test_viewer with py_mini_racer): 26 passed, none skipped (new ServerTests for SQL args and validation)
• Smoke test: server.py --port 8790 --skip-build, POSTed a SQL request over flows → 200 with a valid asap-stage-pipeline/v1 document (language "sql", 5 physical candidates, P1 selected); a bad column type → 400 with a clear message

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