Don't report shutdown DB interrupts as processing errors

[ouziel-slama]

Problem

Sentry issue API-SERVER-8G: Error processing message: ParseTransactionError('interrupted') in production.

ParseTransactionError('interrupted') is an apsw.InterruptError (whose str() is exactly "interrupted") wrapped at blocks.py:260. It is triggered by a db.interrupt() that aborts an in-flight SQLite query.

Chain

1. RawMempoolParser shares the same DB connection as the watcher (RawMempoolParser(self.db)).
2. On shutdown, BlockchainWatcher.stop() → mempool_parser.stop() → db.interrupt() on that shared connection.
3. If the watcher is mid-parse inside receive_message (receive_rawblock/receive_rawtx → parse_tx), the query is aborted → InterruptError("interrupted") → ParseTransactionError("interrupted").
4. receive_multipart logged it as an error, sent it to Sentry, and re-raised to force a "fail loud" restart — of a process that was already stopping.

This is benign teardown noise: no block/tx is corrupted (the supervisor restarts catch_up() from scratch anyway).

Fix

Guard the receive_multipart exception handler with stop_event: during shutdown, log the interrupt at debug and return quietly instead of paging Sentry / re-raising. The fail-loud path is preserved for genuine processing failures (when stop_event is not set).

Tests

• New test_receive_multipart_swallows_interrupt_during_shutdown: with stop_event set, a ParseTransactionError("interrupted") is neither re-raised nor sent to Sentry.
• Existing test_receive_multipart_message_processing_error still asserts the fail-loud re-raise when not shutting down.

Release notes updated in release-notes/release-notes-v11.1.1.md.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.22%. Comparing base (3f08503) to head (50b77c2).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3441      +/-   ##
===========================================
- Coverage    91.38%   91.22%   -0.17%     
===========================================
  Files          114      114              
  Lines        16296    16299       +3     
===========================================
- Hits         14892    14868      -24     
- Misses        1404     1431      +27     

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