adds :wrap_handler() and :finally()

[lePereT]

What type of PR is this?

• 🍕 Feature
• ✅ Test

Description

Extends the core event system in fibers.op with CML-style exception handling and cleanup combinators.

• Adds Event:wrap_handler(handler) for post-synchronisation exception recovery.
• Adds Event:finally(cleanup) for guaranteed cleanup on both success and failure paths.
• Updates compile_event to carry handler chains and apply them in innermost-first order.
• Refactors bracket to use finally for unified resource cleanup.
• Introduces corresponding tests in tests/test_op.lua covering nested wrap_handler, builder errors, and finally semantics.

Related Issues, Tickets & Documents

N/A

Screenshots/Recordings

N/A

Manual test

• 👍 yes

Manual test description

Executed tests/test_op.lua; all new and existing cases pass, confirming correct behaviour of wrap_handler nesting and finally cleanup logic.

Added tests?

• 👍 yes

Added to documentation?

• 🙅 no documentation needed

[optional] Are there any post-deployment tasks we need to perform?

None.