[magnusp]

Closes #37. Part of #54.

What changed

• Replaced the single-FROM parser in SqlTableReference with a resolver that
  returns an origin table for every result column position. It handles simple
  selects, aliases, explicit and comma joins, FROM subqueries, scalar
  subqueries, CTEs, the leftmost branch of a compound SELECT, INSERT /
  UPDATE / DELETE ... RETURNING, and views.
• Views resolve through their definition to the base table that supplies each
  column, including nested views and explicit view column lists.
• LibsqlResultSetMetaData now keeps a per-column origin table instead of one
  table context. getTableName, isNullable, and isAutoIncrement read that
  column's origin and load each distinct table or view once.
• Table definitions are loaded in pragma_table_info column order so *
  expansion and view columns keep their declared order.
• Documented the supported and unsupported shapes in the SqlTableReference
  class Javadoc.
• Added behavior tests per shape: alias, join, subquery, RETURNING (including
  an aliased RETURNING column), and view. Pinned the unsupported expression and
  literal shapes to an empty table name and columnNullableUnknown.
• Split the shape coverage into one commit per shape.

Contract decision

Match xerial 3.53.4.0. getTableName reports the origin table that SQLite's
sqlite3_column_table_name would report, so aliases, joins, subqueries,
RETURNING, and views all keep their base table. A view reports its base table,
not the view name. Nullability follows xerial's rule: look up the result label
in the origin table and report columnNoNulls / columnNullable; an alias
whose label is not a column of the origin table is columnNullable.

getTableName no longer requires the output label to be a column of the
resolved table. That requirement was why select a as z from w returned "".

Evidence

Failing before the fix (new tests on unmodified origin/main):

$ ./mvnw -pl libsql-jdbc -am -Dtest=LibsqlResultSetMetaDataTest \
    -Dsurefire.failIfNoSpecifiedTests=false test
[ERROR] Tests run: 22, Failures: 6, Errors: 0, Skipped: 0
[ERROR]   resolvesAliasTableNameAndNullability:333 expected: "w" but was: ""
[ERROR]   resolvesAliasedReturningTableNameAndNullability:381 expected: "w" but was: ""
[ERROR]   resolvesJoinTableNamesAndNullability:344 expected: "w" but was: ""
[ERROR]   resolvesReturningTableNameAndNullability:368 expected: "w" but was: ""
[ERROR]   resolvesSubqueryTableNameAndNullability:357 expected: "w" but was: ""
[ERROR]   resolvesViewTableNameAndNullability:392 expected: "w" but was: "v"

Passing after the fix:

$ ./mvnw -pl libsql-jdbc -am test
Tests run: 103, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

$ ./mvnw -pl libsql-conformance -am verify
Tests run: 117, Failures: 0, Errors: 0, Skipped: 1
BUILD SUCCESS

Includes the vendored xerial RSMetaDataTest (13 tests) against live sqld.

$ DOCKER_CONFIG=/tmp/docker-config ./mvnw -pl libsql-itests -am verify
Tests run: 18, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

I also ran a temporary live-sqld probe (removed before committing) asserting
getTableName and isNullable for alias, join, subquery, CTE, UNION,
RETURNING, view, aliased view column, and expression shapes. All matched the
expected xerial values.

$ ./mvnw spotless:apply
BUILD SUCCESS (no formatting changes)

Deviations

Supported shapes match xerial 3.53.4.0.

For unsupported shapes (expressions and literals) this driver reports
getTableName == "" and isNullable == columnNullableUnknown. xerial reports
the same empty table name but columnNullable for those columns because it
treats missing SQLite column metadata as nullable. The issue explicitly asks
unsupported shapes to return documented empty or unknown values, and an
expression has no table column whose nullability could be known, so this PR
keeps the honest unknown value.