Fix/caller disconnect callee crash

[markope]

Fix: Prevent callee session crash when caller disconnects during RPC

Description

This PR fixes a bug where the callee's session crashes when the caller disconnects during an in-flight RPC call.

Problem

When a WAMP caller disconnects while waiting for an RPC response (e.g., browser page reload), the callee receives an exception and its session is terminated. This happens because:

1. The router checks if the callee supports call_canceling
2. If not supported, it skips cleanup entirely (continue)
3. Stale invocation tracking data remains in memory
4. When callee returns a result, it finds the caller's transport is None
5. This causes an error that crashes the callee's session

Solution

Always clean up invocation tracking when caller disconnects, regardless of call_canceling support:

# BEFORE (buggy): Skip cleanup if callee doesn't support canceling
if not callee_supports_call_canceling:
    continue  # BUG: leaves stale invocation tracked!

# AFTER (fixed): Always clean up, conditionally send INTERRUPT  
cleanup_invocation_tracking()  # Always executed
if callee_supports_call_canceling:
    send_interrupt()  # Only if supported

Changes

• File: src/crossbar/router/dealer.py
• Method: Dealer.detach()
• Moved cleanup code before the call_canceling check
• INTERRUPT message is still only sent if callee supports it
• Added clarifying log message for non-canceling case

Impact

• Callees without call_canceling: No longer crash when caller disconnects; they complete normally and the result is silently discarded
• Callees with call_canceling: Behavior unchanged (receive INTERRUPT as before)
• Backward compatible: No breaking changes

Testing

• New test: test_caller_detach_cleans_up_invocation_tracking_without_cancel_support
  • Verifies invocation tracking is cleaned up when caller disconnects
  • Callee without call_canceling support
  • Confirms callee can return result without crash (result silently discarded)

Existing tests cover related scenarios:

• test_caller_detach_interrupt_cancel_not_supported
• test_caller_detach_interrupt_cancel_supported

Fixes

#2133

[markope]

closed and replaced by #2153 due to process reasons