v1.108.265 - Retrieval confidence grades ranking quality, not units

Found while fixing the same defect in jdocmunch (#106) and checking whether the siblings shared it. jcodemunch did. jdatamunch does not — it has no confidence surface and blends linearly — so this is a two-server defect, not a suite-wide one.

The defect

compute_confidence's strength sub-signal squashes a raw top-1 score through a curve that was hardcoded to the BM25 scale, applied to every caller. Measured on identical relative separation between the top two results:

scorer	top-1	strength	confidence
BM25	20.0	0.9933	0.223
WRR fusion	0.0492	0.0122	0.048
cosine	0.82	0.1854	—

Four scales reach that function here, not two. Besides fusion and cosine, sort_by="centrality" ranks by PageRank, which sums to 1 across files — so the most central symbol in a repository was graded at a strength near 0.01.

Two consumers read the number, and the weight tuner is the smaller one:

• verdict.STATE_LOW_CONFIDENCE gates whether a scan may assert an answer. Fusion and semantic searches were being downgraded for arithmetic rather than for evidence.
• WeightTuner adjusts semantic_weight from the difference in mean confidence between semantic_used groups. A scale gap of roughly 0.5 dwarfs its 0.05 decision threshold, so it reads "semantic hurts" and steps the weight down toward its floor on any mixed-mode ledger. Measured end to end in the sibling before this port: seven consecutive downward rounds, on data where the semantic channel was doing the work.

The fix

Each caller now passes the ceiling of whichever scorer produced its scores.

• New signal_fusion.fused_score_ceiling(channels, smoothing, weights) returns sum(weights) / (k + 1) — the score a symbol ranked first in every channel actually reaches. It shares one weight-resolution helper with fuse, and a parametrized test fuses a perfect-consensus set and asserts the top score equals the ceiling, so the two cannot drift apart.
• The sibling's 1/(k+1) constant would have been wrong here. jdocmunch normalizes its fusion weights to sum to 1; these are not normalized, so with three unit-weight channels the correct ceiling is three times that. A test asserts the sibling's constant is not the answer. Suite parity is a contract to port, not code to copy.
• sort_by="centrality" uses the most central file in the repository as its ceiling. combined stays BM25-scaled, since PageRank enters it multiplied by 100.
• The BM25 path is unchanged. 1 - exp(-3t/12) is algebraically identical to the old 1 - exp(-t/4), asserted at six score values, so only the callers that were wrong move. An unknown or non-positive ceiling falls back to BM25, so a caller that passes none is unchanged rather than newly wrong.

Upgrade note: _meta.confidence moves upward for fusion, semantic and centrality searches, and some low_confidence verdicts move with it. If you gate anything on a confidence threshold, re-check it.

Also in this release

Two commits made after the 1.108.264 tag ride along: ruff's rule select is now pinned explicitly rather than inherited from the installed version, and the file-IO encoding scanner locates a mode argument by value rather than by position.

Verification

test_confidence_score_scale.py (17 tests). Suite 7394 passed / 7 skipped, a delta of exactly the new file — and no existing test pinned a fusion or semantic confidence value, which is why a five-fold mis-scaling shipped and survived.

Built and verified from an isolated git worktree at the release commit, with the sdist and wheel audited for content rather than assumed clean.