[asukaminato0721]

Summary

Code after a statically true loop without a break is unreachable. Record flow termination after these loops, including retry loops that can exit only through return or an exception.

Preserve exception termination so an enclosing context manager can suppress it. Keep environment-dependent loop conditions from producing unreachable warnings in code that can execute in another Python environment.

This changes the default-enabled unreachable-code diagnostic. It is independent of the attribute initialization check in #4326. Direct tests cover retry loops, infinite loops, environment-dependent conditions, and suppressed exceptions.

• I am a human, and I fully understand the code I am submitting.

Test Plan

• 532 related tests passed, including scope, loops, branching, returns, delayed inference, hover, and ParamSpec retry coverage.
• Formatting and lint checks passed. Clippy reports existing warnings in unchanged code.

[meta-codesync]

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[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

============================================================
SUMMARY
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Total: +5 new errors, -2 fixed errors
By preset: +5/-2 (default), +5/-2 (strict)

Projects with changes (4):
  psycopg: +2 -0
  manticore: +1 -2
  poetry: +1 -0
  cvxpy: +1 -0
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FULL DIFF DETAILS
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psycopg (https://github.com/psycopg/psycopg)
+ ERROR psycopg/psycopg/types/multirange.py:333:9-19: This code is unreachable [unreachable]
+ ERROR tests/pq/test_pgconn.py:44:5-46:61: This code is unreachable [unreachable]

manticore (https://github.com/trailofbits/manticore)
+ ERROR tests/auto_generators/trace.py:174:1-46: This code is unreachable [unreachable]
- ERROR tests/ethereum/test_general.py:1723:26-32: `result` may be uninitialized [unbound-name]
- ERROR tests/ethereum/test_general.py:1779:26-32: `result` may be uninitialized [unbound-name]

poetry (https://github.com/python-poetry/poetry)
+ ERROR src/poetry/utils/authenticator.py:301:9-74: This code is unreachable [unreachable]

cvxpy (https://github.com/cvxpy/cvxpy)
+ ERROR cvxpy/utilities/power_tools.py:610:5-69: This code is unreachable [unreachable]