fix(pg): closing schema browser tabs or stats view force-closes the shared read-only session #1237

Part of #1212. Follow-up to #1215 and #1236.

Problem

Closing any of the PostgreSQL schema object browser views or the stats view while loading force-closes the shared readOnly session of the database.

In lib/features/postgresql/postgres_browser_views.dart:

• PostgresIndexListView.dispose() (lib/features/postgresql/postgres_browser_views.dart:51)
• PostgresTriggerListView.dispose() (lib/features/postgresql/postgres_browser_views.dart:231)
• PostgresTypeListView.dispose() (lib/features/postgresql/postgres_browser_views.dart:403)
• PostgresExtensionListView.dispose() (lib/features/postgresql/postgres_browser_views.dart:555)
• PostgresFdwListView.dispose() (lib/features/postgresql/postgres_browser_views.dart:701)

In lib/features/postgresql/postgres_stats_view.dart:

• PostgresStatsView.dispose() (lib/features/postgresql/postgres_stats_view.dart:69)

All 6 views contain:

if (_loading) {
  PostgresService.instance.interrupt(
    widget.connectionRow,
    database: widget.database,
    mode: PgSessionMode.readOnly,
  );
}

PostgresService.instance.interrupt removes the pooled entry and calls forceClose() on the shared connection. That connection is shared with the object tree, open table tabs, ERD/relations view, other browser views and MCP calls.

Effects:

• Closing any of these views while loading drops in-flight queries across other views and MCP with Not connected to PostgreSQL.
• Triggers reconnect race conditions (fix(db): concurrent connect() on a pooled connection leaks sockets and SSH tunnels, a failed attempt drops the working session #1214) and lease release bugs (fix(db): a lease released after interrupt decrements the pool entry that replaced it #1213).

Scope

• Remove if (_loading) PostgresService.instance.interrupt(...) from dispose() across all 5 views in postgres_browser_views.dart and PostgresStatsView in postgres_stats_view.dart.
• dispose() should only release the acquired lease (_lease?.release()), matching the pattern established for tables (fix(db): closing a table tab force-closes the read-only session other views are using #1215) and routine/sequence views (fix(pg): closing a sequence or routine view releases its lease without interrupting the shared session (#1215) #1236).
• An in-flight query should finish or time out on its own.

Acceptance

• Closing PostgresIndexListView, PostgresTriggerListView, PostgresTypeListView, PostgresExtensionListView, PostgresFdwListView, or PostgresStatsView while loading does not call PostgresService.interrupt and leaves the shared session intact.
• Existing tests pass without regressions.