fix: table-level PRIMARY KEY(col) rowid alias reads back NULL when the table has other columns (#686)

[dpsiderius]

What

src/schema/ddl_reader.rs::rowid_alias_from_sql required a table-level
PRIMARY KEY (col) to name the table's only column before treating it
as a rowid alias. That is not SQLite's rule: a second column does not
rule it out. The reader now matches the named column against the column
list directly.

Before/after (measured against the pinned oracle)

$ sqlite3 m1.db "CREATE TABLE m1 (a INTEGER, b TEXT, PRIMARY KEY (a));
                 INSERT INTO m1 VALUES (1,'x');"
$ sqlite3 m1.db "SELECT a, b FROM m1"
1|x
$ sqlite-rs query m1.db "SELECT a, b FROM m1"   # before: |x  (a NULL)
                                                  # after:  1|x

Test matrix: table-level PK on a single INTEGER column with/without other
columns, non-INTEGER typed, composite (no alias), column-level control
(regression guard, was already correct).

Test plan

• tests/corpus/rowid_alias_test.rs — full rule table, oracle-diffed.
• make test, make lint, make test-corpus, make check-mvl-limit, make check-mod-files, make assurance all pass.

Refs: 001/Req-*, #705
Closes #686

spend: matched estimate