Adopt server-provided connection id for managed-db tables; remove __db_ workaround

[eddietejeda]

Follow-up — blocked on server change

Tracking issue to revisit the CLI once hotdata-dev/www.hotdata.dev#234 ships. Do not action until the server change lands.

Once the server exposes a real connection id for managed-database tables (preferred: a connection_id/database_id field on each information_schema TableInfo; alternative: db-scoped connections surfaced in connections list), the CLI should adopt it and drop the string-convention workaround.

The server change is additive/backward-compatible, so nothing breaks if this lags — this is cleanup to adopt the improvement, not a forced migration.

Work, by which server option lands

If information_schema gains connection_id/database_id (preferred):

• Add the field to InfoTable in src/indexes.rs and have scan_connection_id use the row's own id directly.
• Delete the __db_<suffix> ↔ dbid<suffix> reverse-transform and the per-database databases get round-trips introduced by the indexes list (unscoped) misses managed-database indexes #168 stopgap.
• To read the typed field, bump the hotdata SDK (currently 0.3.1), or switch collect_tables to the untyped seam GET (get_json) with the CLI's own struct to avoid an SDK bump.

If db-scoped connections are instead surfaced in connections list:

• Verify what key the entries expose — connection_lookup matches on connection name, which may not equal the __db_* label emitted by information_schema. Adjust the matched key accordingly (still a code change).

Acceptance

• Unscoped hotdata indexes list shows managed-database indexes (the gap in indexes list (unscoped) misses managed-database indexes #168) without the encoding-convention coupling.
• The indexes list (unscoped) misses managed-database indexes #168 stopgap code (if merged by then) is removed.

Refs

• Server change (blocker): hotdata-dev/www.hotdata.dev#234
• CLI gap + stopgap: indexes list (unscoped) misses managed-database indexes #168
• Original scoped-path fixes: indexes list (connection-wide) returns empty for managed DuckLake connections #161, fix(indexes): list indexes for a database-scoped connection #164