Fix rowid pk and last_rowid regressions in insert/upsert

[simonw]

Refs:

• Regression: last_rowid is None after an ignored insert #783
• Regression: rowid primary key rejected by upsert(pk=) #781
• Release sqlite-utils 4.0 stable #769

Two behaviour regressions in the 4.0 insert/upsert rewrite broke callers
(notably Datasette's write API) that operate on tables without an explicit
primary key. Both are fixed here with regression tests.

1. rowid (and its aliases rowid/oid) were rejected as a primary key.
   Table.pks already reports ["rowid"] for a rowid table, but the new pk
   validation raised InvalidColumns because rowid is not listed among the
   table's columns, and the insert success path then raised KeyError when
   looking up the pk value. rowid aliases are now accepted for rowid tables
   and resolve directly to the rowid.

2. An ignored insert (INSERT OR IGNORE that matched an existing row) no
   longer populated last_rowid, and only set last_pk when an explicit pk=
   was passed. It now locates the existing conflicting row by its primary
   key values and reports that row's rowid and pk, rather than relying on
   the connection's last inserted rowid.

Add a shared ROWID_ALIASES constant for the rowid alias names.

Co-Authored-By: Claude Opus 4.8 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_01E7af8SxFZqiCerJB6MqKnY

---

📚 Documentation preview 📚: https://sqlite-utils--782.org.readthedocs.build/en/782/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.46%. Comparing base (d314d04) to head (d53e3cb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #782      +/-   ##
==========================================
+ Coverage   95.15%   95.46%   +0.31%     
==========================================
  Files           9        9              
  Lines        3712     3727      +15     
==========================================
+ Hits         3532     3558      +26     
+ Misses        180      169      -11     

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[simonw]

That last commit is because I prompted:

The change in db.py is quite complex check if the tests fully cover that using coverage