Reduce SQLite table probes during store open

[forest-savage1234]

Summary

• Read the SQLite table-name set once per Open() and query row counts only for container tables that exist.
• Keep the next sequence number at zero for absent container types, preserving current read and write behavior.
• Add a regression that asserts row-count queries are issued only for present tables.

Closes #4

Validation

• tests.sqlite_store — 21 passed.
• git diff --check.
• The issue's controlled benchmark reports 89.75% fewer schema/probe queries and a 55.8–57.0% reduction in time spent in Open() for two images.

Scope notes

The patch intentionally leaves the existing _HasTable call inside row counting for present tables; removing that is separate scope.

[joachimmetz]

@forest-savage1234 thanks for the proposed changes, what is the status of this PR? Still draft?

[joachimmetz]

No response from original reporter, considering this PR still being worked on. Closing