feat: back-port inline window-function grammar (OVER (PARTITION BY … ORDER BY …)) from t-rust-db/db-core parser::row

[iheitlager]

Description

t-rust-db/db-core's parser::row is a port of this crate's src/parser, and per t-rust-db/db-core ADR 0005 this grammar is the canonical one. The port has since grown a feature this crate lacks (t-rust-db/db-core#74/#67): inline window functions.

• ast::Expr::FunctionCall { …, over: Option<WindowDef> }, WindowDef { partition_by: Vec<Expr>, order_by: Vec<OrderingTerm> } with Display
• grammar.rs: OVER ( [PARTITION BY expr, …] [ORDER BY term, …] ) parsed; OVER <name>, frame clauses (ROWS/RANGE/GROUPS) and FILTER (…) stay Unsupported with specific messages
• Tests: window_function_over_partition_and_order_by_roundtrips, window_over_named_window_reference_is_unsupported, window_frame_clause_is_unsupported, window_filter_clause_is_unsupported

Back-port it here so diff -r sqlite-rs/src/parser db-core/src/parser/row returns to zero (t-rust-db/db-core#84 records the rule: grammar changes land here first, or are back-ported in the same window). tests/unit/parser.rs line ~677 currently asserts OVER is unsupported and needs to follow. The codegen/VDBE side is a separate matter (spec 009 V9) — this ticket is grammar + AST + printer only; the planner may keep rejecting over for now.

Complexity

Estimate: small — ~150 lines, all already written in db-core; port verbatim.

Acceptance Criteria

• src/parser/{ast,grammar,printer}.rs match db-core's parser::row for the window-function parts
• The four db-core tests pass here; tests/unit/parser.rs's OVER expectation updated
• make check-grammar-drift green (sqlite.ebnf gains the over_clause/window_defn rules with parse.y citations, per the grammar convention)

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🤖 Analysis by Claude