Self-analysis: remove remaining false positive and make --warnings-only output actionable

[SizzleUnrlsd]

Description

When the analyzer runs on itself, two usability/quality issues remain:

1. --warnings-only still prints all functions, even those without warnings/errors, which creates noise and slows down triage.
2. A false positive DuplicateIfCondition is reported in stripIntCasts(...) (InvalidBaseReconstruction.cpp) due to a redundant conditional return pattern.

Expected behavior:

• In --warnings-only, human output should list only functions that have at least one non-info diagnostic.
• No unreachable else-if branch warning should be emitted for stripIntCasts(...).

Acceptance criteria:

• --warnings-only output is function-filtered by remaining diagnostics.
• Self-analysis of src/analysis/InvalidBaseReconstruction.cpp no longer emits that warning.
• Regression tests cover the --warnings-only function-listing behavior.