rowid-keyed tables unsupported: rows are keyed by primary key, not rowid

DoltLite keys user-table rows in its prolly tree by the user's primary key
columns rather than by SQLite's auto-allocated rowid (since #358). Rowid is
allocation-order dependent and therefore history dependent, which is a hard
incompatibility with the Dolt model: two branches that independently insert
identical rows have to produce identical row identities, and a
content-addressed tree cannot do that if the key is "whichever integer this
connection handed out first".

Consequences, all of which inherited SQLite testfixture suites exercise:

- a table without an explicit INTEGER PRIMARY KEY is auto-converted to
WITHOUT ROWID, so `rowid` is not an addressable column — `WHERE rowid = N`
and `ORDER BY rowid` error with "no such column: rowid"
- an unordered `SELECT` returns user-PK order where stock SQLite returns
rowid (insertion) order
- `PRAGMA table_info` reports non-PK columns differently for auto-converted
WITHOUT ROWID tables
- AUTOINCREMENT and `sqlite_sequence` behavior tied to rowid allocation
- foreign key `SET NULL` / `SET DEFAULT` whose triggering DELETE addresses
parent rows by rowid

This is the single largest rationale in
`test/known_testfixture_divergences.txt` — its header block has documented it
at length, but with no issue to point at, so per-suite rows in
`test/known_testfixture_exception_inventory.txt` had nowhere to attribute it.
This issue is that anchor.

Not expected to be fixed; rowid-keyed storage is incompatible with the
version-control model rather than merely unimplemented.

### Attribution status

Attributed so far are the suites whose own recorded reason names rowid
explicitly (25 divergence suites plus `btreefault`, `incrblob`, `walbig`).
That is a floor, not the true count: most rowid-driven suites rely on the
header block instead of repeating the reason inline. Widening the attribution
is a triage pass over the remaining `intentional` rows and should not be
guessed at in bulk.

Start with the rowid rationale in test/known_testfixture_divergences.txt and the intentional rows in test/known_testfixture_exception_inventory.txt. Review remaining entries for suites whose divergence is caused by rowid behavior, then attribute only supported cases in the inventory and preserve the header explanation; done means the issue is the anchor without speculative bulk attribution.

Written by the indexing model from the issue text.