feat(frontend): run statement at cursor on Cmd+Enter

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Demo :

demo.mov

Summary

• Cmd+Enter, Ctrl/Cmd+F5, and the Explain button now run/explain the SQL statement the cursor is currently inside when nothing is selected, instead of running the whole file or popping open a "pick a statement" modal — matching TablePlus/DataGrip behavior.
• A subtle, theme-aware background highlight shows which statement is armed to run whenever there's no selection, and disappears the instant you make a selection.
• Whole-file / multi-statement execution is still available by selecting all text first (Cmd+A) — no new UI needed for that.
• Explaining a non-explainable statement (e.g. DDL) now shows a warning alert instead of silently doing something unexpected.
• Fixes two related bugs surfaced by this workflow: running two different statements/tables back to back on the same tab could leave stale primary-key/column metadata from the previous statement applied to the new one (breaking inline cell editing with a misleading "column not editable" error naming the wrong table), and every pagination/refresh action (including the post-edit-save refresh) re-sent the entire editor buffer instead of the single statement that produced the current result — which Postgres rejects as "cannot insert multiple commands into a prepared statement" whenever the buffer holds more than one statement.

Details

• Added findStatementAtOffset to sqlSplitter, resolving which statement a cursor offset falls inside using the splitter's existing (previously unused) per-statement range data. A cursor in the gap between two statements resolves to the preceding one; a cursor before the first statement does nothing.
• handleRunButton/handleExplainButton in Editor.tsx now resolve the statement at the cursor via a shared helper instead of falling back to the whole file.
• SqlEditorWrapper gained an opt-in dialect prop that drives the cursor-statement highlight decoration; other consumers of the component are unaffected since they don't pass it.
• runQuery now tracks the exact statement it last ran per tab and a per-tab generation counter, so async responses (PK/column metadata fetch, the main query result) from a superseded run are dropped instead of clobbering a newer run's state, and pagination/refresh call sites now re-run "whatever's currently shown" instead of the raw multi-statement editor buffer.
• QuerySelectionModal is left in the codebase but no longer reachable from the Run/Explain paths.

Test plan

• pnpm test — 2797 tests pass, including new coverage for findStatementAtOffset (statement boundaries, gaps between statements, before/after the statement list, single-statement files)
• pnpm typecheck / eslint clean
• Manual pass in the running app: multi-statement tab, cursor in different statements with no selection (highlight + Cmd+Enter/F5/Explain all target the right one), select-all still runs everything, editing a cell after running a single statement out of a multi-statement tab, paging through results from that same scenario, and saving an edit — all previously reproduced the "multiple commands in a prepared statement" error and now work correctly

Let me know if you'd like it trimmed down or adjusted before you post it.