bug: two oracle divergences the parser tickets left behind (#696/#698 scope gaps) #725

Both live in src/parser/, both are that ticket's own stated scope rather than
new work, and one PR closes both.

2a — an unterminated block comment is rejected where SQLite ignores it.

input: "/* unterminated"                     oracle rc=0    ours rc=1
input: "CREATE TABLE t(a); /* unterminated"   oracle rc=0    ours rc=1

In the second case the table IS created by both engines, so we do the work and
then report failure — the worst combination for a script runner. Same on
origin/main: PR #713 fixed five comment forms and left this sixth diverging.
Tokenizer::tokenize emits a TokenKind::Error for an unterminated comment and
skip_leading_trivia does not treat that span as trivia, so the fragment
survives as a bogus statement.

2b — bare aliases without AS reject all 89 fallback keywords. PR #714
accepts them via AS but disables them for bare aliases entirely, because
allowing them broke NATURAL JOIN/LEFT JOIN. Correct for the ~7 join
keywords, overbroad for the other ~82:

SELECT key.a FROM t key      oracle: 7                      ours: syntax error
SELECT first.a FROM t first  oracle: 7                      ours: syntax error
SELECT left.a FROM t left    oracle: error (join keyword)    ours: error   (correct)

Verified for key first row match glob like offset view temp. #696's own
acceptance criteria asked for all 89 to work as aliases.

Scope: an unterminated block comment is trivia to end-of-input, keeping
test_malformed_input_never_panics passing and comments inside string literals
literal. Permit fallback keywords as bare aliases except the join keywords
(CROSS FULL INNER LEFT NATURAL OUTER RIGHT), matching parse.y's precedence.
Correct .openspec/grammar/sqlite.ebnf, whose result-column/table-ref rules
permit a bare identifier (now including fallback-keyword) without encoding
the AS-only carve-out the code enforces; make check-grammar-drift must pass.
Oracle-diff both comment forms, an unterminated comment mid-script and inside a
string literal, and each of the 89 words as a bare alias.

Note: 2b's fully-qualified form (SELECT key.a FROM t key) cannot be tested
end to end until ticket 1b lands, since alias-qualified references fail for a
plain alias too. The unqualified form (SELECT a FROM t key) is testable now.

Complexity

Estimate: small-medium
Reasoning:

Refs: 002/Req-1, 002/Req-2, #696, #698, #713, #714