feat(explorer): use uncertainties for analysis propagation

[Rajesh270712]

Summary

• Adds uncertainties~=3.2 to deltakit-explorer.
• Uses ufloat, unumpy, and correlated_values for LEPPR, log-fidelity, and lambda uncertainty propagation.
• Keeps public return values as plain floats/arrays and adds focused parity tests.

Links

• Addresses request: use uncertainties instead of computing standard deviations manually #215
• UnitaryHack bounty listing: https://unitaryhack.dev/bounties/

Problem

Issue #215 asks for the analysis helpers to use uncertainties instead of maintaining standard-deviation propagation formulas manually. The existing LEPPR/log-fidelity/lambda paths computed propagated errors by hand, which made the formulas harder to audit and extend.

Fix

This PR adds uncertainties to the explorer package and delegates the affected propagation steps to uncertainties helpers. The external API shape is unchanged: callers still receive floats or NumPy arrays rather than uncertainties objects.

Validation

• uv run --group test pytest deltakit-explorer/tests/analysis/test_leppr.py deltakit-explorer/tests/analysis/test_lambda.py deltakit-explorer/tests/analysis/budget/test_post_processing.py -q -> 6063 passed in 11.25s
• uv run --group lint ruff check deltakit-explorer/src/deltakit_explorer/analysis/_leppr.py deltakit-explorer/src/deltakit_explorer/analysis/_lambda.py deltakit-explorer/tests/analysis/test_leppr.py deltakit-explorer/tests/analysis/test_lambda.py -> All checks passed!
• uv run --group lint mypy --config-file deltakit-explorer/pyproject.toml deltakit-explorer/src/deltakit_explorer/analysis/_leppr.py deltakit-explorer/src/deltakit_explorer/analysis/_lambda.py -> Success: no issues found in 2 source files
• uv run --group lint deptry deltakit-explorer/src --config deltakit-explorer/pyproject.toml -> Success! No dependency issues found.
• uv run python -c "import uncertainties; import deltakit_explorer.analysis._leppr; import deltakit_explorer.analysis._lambda; print(uncertainties.__version__)" -> 3.2.3
• git diff --check origin/main...HEAD -> passed with no output

Risk Notes

• I did not run the full repository test suite; validation covered the changed analysis tests, an adjacent budget post-processing guard, changed-file lint, changed-source typing, deptry, import check, and diff check.
• uncertainties does not ship type stubs, so the mypy configuration includes a narrow missing-import override for that dependency.

[CLAassistant]

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