fix: don't surface a ClickHouse ARRAY JOIN operand as a table read

[takaebato]

Summary

Fixes a follow-up noted in #55: a ClickHouse ARRAY JOIN operand was surfaced as
a (spurious) table read.

sqlparser parses the operand of ARRAY JOIN / LEFT ARRAY JOIN / INNER ARRAY JOIN as a TableFactor::Table, indistinguishable from a real table — so
SELECT s FROM t ARRAY JOIN arr reported a phantom read of a table arr.
(ClickHouse's ARRAY JOIN operand is always an array — a column or an array
expression — never a table.)

This binds the ARRAY JOIN operand as an opaque unnest (a TableFunction, so no
table read):

• A plain array column (arr / t.arr) reads as a column of the left
  relation: read_tables no longer includes it (SELECT s FROM t ARRAY JOIN arr
  → [t], not [t, arr]), and t.arr surfaces as a column read.
• An array expression (arrayConcat(t.a, t.b)) reads its argument columns
  (t.a, t.b) — not the function name.
• The unnested output (AS x, else the operand's own name) is exposed as a
  synthetic column, so a reference to it no longer leaks as a phantom t.x read.

Edge cases covered on review:

• The UPDATE target's join clause takes the same special case:
  UPDATE t ARRAY JOIN arr SET a = 1 no longer reads a phantom arr table
  (and t correctly surfaces as a read — the unnest references the write
  target's own data).
• A non-Table operand (a derived subquery — invalid ClickHouse but sqlparser
  parses it) falls back to the normal factor path, so its reads survive instead
  of being silently dropped.
• Pipe joins (|> JOIN) cannot parse an ARRAY JOIN operator — unreachable.

Tests: updated the ARRAY JOIN arm coverage (now expects the operand column read),
plus table-level "operand is not a read table" (SELECT and UPDATE), "alias does
not leak as a phantom column", "expression operand reads its arguments", and
"derived operand keeps its reads" tests. All gates green (fmt / clippy /
test --all / doc).

Left as-is (both exotic): the analogous multi-table DELETE-target path
(DELETE … USING t ARRAY JOIN arr), and a multi-array ARRAY JOIN a, b — which
sqlparser parses as a comma-join, so b still looks like a table.

🤖 Generated with Claude Code

[github-actions]

✅ PR title follows the Conventional Commits spec.

[codecov]

Codecov Report

❌ Patch coverage is 96.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.77%. Comparing base (b0eb0dd) to head (a12b033).

Files with missing lines	Patch %	Lines
sql-insight/src/resolver/binder/query.rs	95.23%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #57   +/-   ##
=======================================
  Coverage   94.76%   94.77%           
=======================================
  Files          27       27           
  Lines        5542     5590   +48     
  Branches     5542     5590   +48     
=======================================
+ Hits         5252     5298   +46     
- Misses        212      214    +2     
  Partials       78       78           

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