fix: harden neutralization and Baostock data handling

[redamancy231-create]

What changed

This revision rebases the contribution onto the current main and keeps only the new fixes beyond #33 and #34.

• use a scale-relative degeneracy guard in industry neutralization, avoiding amplified float32 noise without suppressing genuinely small signals
• expand neutralization tests for orthogonality, rank-deficient designs, perfect fits, small-scale signals, masks, shapes, and dtypes
• keep Baostock VWAP consistent with forward-adjusted OHLC through the typical-price proxy
• reject unavailable raw VWAP explicitly instead of mixing adjusted and unadjusted data
• normalize and validate complete sh./sz. ticker codes with regression tests

The previously merged Baostock report, dependency declarations, and CLI integration remain unchanged.

[initial-d]

Thanks for the follow-up fixes. I amended the PR before merge to keep the contribution focused and numerically safe:

• rebased the branch onto the current main and removed the duplicated test: add neutralize module tests (11 cases) #33/feat: add Baostock A-share data source + validation report (25 stocks, 2021-2024) #34 content
• changed the absolute neutralization cutoff to a scale-relative degeneracy guard, so small but valid signals are not suppressed
• expanded the tests to cover orthogonality, true rank deficiency, perfect fits, scale invariance, masks, shapes, and dtypes
• kept Baostock VWAP on the forward-adjusted OHLC basis and rejected unavailable raw VWAP explicitly
• strengthened ticker validation to require complete sh./sz. plus six-digit codes
• cleaned the PR title and commit metadata

CI is green on Python 3.9, 3.10, and 3.11.

[initial-d]

Post-merge history correction: the contributor branch changed again while the verified CI run was in progress, so the initial merge briefly referenced an unreviewed duplicate-history commit. main has been corrected with --force-with-lease to the reviewed tree.

The authoritative commits are now:

• reviewed contribution: c2be285
• reachable fix: harden neutralization and Baostock data handling #35 merge on main: 6a3eb39

The resulting tree contains the focused six-file fix described above and no AI-tool trailer. GitHub revoked maintainer write access to the fork branch after merge, so the PR head ref itself could not be rewritten again; this note records the discrepancy explicitly.