[epic] ClickHouse parser gaps from QA sweep

[ajitpratap0]

Context

Exhaustive QA against the ClickHouse dialect (gosqlx.ParseWithDialect(..., DialectClickHouse)) ran 83 representative real-world queries. 44/83 (53%) pass. This epic tracks the 9 distinct bugs that account for the 39 failures.

QA harness: pkg/sql/parser/clickhouse_qa_test.go (build tag `qa`, excluded from CI). Run with:
```
go test -tags qa -run TestClickHouseQA -v ./pkg/sql/parser/
```

Tracked bugs (sub-issues will be filed against this epic)

• Nested/parameterised column types — Array(Nullable(T)), Map(K,V), Tuple(...), LowCardinality(String), FixedString(16), CODEC(ZSTD(3), Delta), Distributed('cluster', db, t, key), ReplicatedMergeTree('path','{r}'). Root cause: pkg/sql/parser/ddl_columns.go:77-102 only handles flat type args. 12 failures, biggest single bug.
• SETTINGS k = v tail clause — unconsumed in SELECT and CREATE TABLE despite keyword being registered.
• Array literal [1,2,3] — only ARRAY[...] form supported.
• TTL DDL clause in column and table position.
• ORDER BY ... WITH FILL — WITH after ORDER BY items mis-routed to the WITH-CTE parser.
• CREATE MATERIALIZED VIEW ... TO/ENGINE variants.
• ROWS not in non-reserved-id allowlist.
• Parametric aggregates fn(p)(args) — e.g. quantileTDigest(0.95)(value).
• INSERT ... FORMAT name tail.

Burndown target

Each PR removes its passing entries from clickhouse_qa_test.go and adds focused regression tests in canonical test files. Target: ≥90% pass rate by end of Wave 4.

Related

• [BUG] multiple errors in ClickHouse dialect #480 (already fixed: table/partition/tables as identifiers — PR fix(parser): allow TABLE/PARTITION/TABLES as identifiers in ClickHouse (#480) #481)