sigker: fix both clippy findings and arm the lint in CI

[AdaWorldAPI]

Summary

Closes TD-SIGKER-CLIPPY-RED-ON-BASE-1. sigker now passes cargo clippy --manifest-path crates/sigker/Cargo.toml --all-targets -- -D warnings, and the lint is gated in CI so it stays that way.

Two findings, not the one the tech-debt entry claimed

#	Site	Lint
1	signature.rs — segment_signature's level-fill loop	needs_range_loop
2	examples/depth_scaling.rs — wrapped doc list continuation	doc list item overindented

Finding 2 was invisible until finding 1 was fixed. -D warnings makes clippy abort at the first error, so the entry's "single site" was a lower bound read off a run that never got past the first failure — not a total. That's recorded in the entry rather than quietly corrected, because the general lesson is worth keeping: a findings count from an aborted run is a floor.

Finding 1's fix is behaviour-identical — level.iter_mut().enumerate(), same traversal, same arithmetic:

for (flat, slot) in level.iter_mut().enumerate() {
    let mut idx = flat;
    ...
    *slot = prod / factorial;
}

The lint is now gated, not just fixed

The sigker CI step added in #1166 was deliberately tests-only, because the crate was clippy-red on arrival and gating it would have failed that PR for a defect it didn't introduce. That reason is gone, so the clippy half is armed here.

This matters more than the fix itself: sigker was unlinted precisely because no CI step reached it — it's workspace-excluded, so root-level cargo clippy never sees it. A lint fix with no gate decays straight back to where it started.

The entry cited the line whose deletion is the fix

Worth flagging as a pattern. TD-SIGKER-CLIPPY-RED-ON-BASE-1 cited signature.rs:133 anchored on for flat in 0..len — and deleting that line is the fix, so applying it made the entry's own citation decay and citation_decay.py fired on it.

An entry that cites the code it wants removed is self-invalidating by construction. Re-anchored on the enclosing function name, segment_signature, which survives its own body being rewritten — the property a citation into mutable source actually needs. That's the second time this session the citation gate has corrected a citation of mine, both times correctly.

One incidental accuracy fix

While rewriting the overindented line, its "7-13× smaller" claim is now qualified as asymptotic (N≥8, ~2× at shallow depth) with a pointer to the crate's own falsifier test compression_at_shallow_depth_is_far_below_the_headline. Same misquote E-A-SKETCH-THAT-MISSED-TWICE-WILL-MISS-A-THIRD-TIME-1 flagged in the ndarray consumer contract — it had propagated here too. Called out because it's a content change on a line I was already editing for the lint, not a silent extra.

Test plan

• cargo clippy --manifest-path crates/sigker/Cargo.toml --all-targets -- -D warnings — 0 errors
• cargo test --manifest-path crates/sigker/Cargo.toml — 62 passed, 0 failed
• cargo fmt --check — clean
• citation_decay.py --since origin/main — 0 new decays (148 pre-existing backlog unchanged)
• append_only_gate.py origin/main — no protected file shrank, 9 checked
• supersession_index.py — current, byte-identical
• plan_dids.py — no added plans
• rust-test.yml parses as valid YAML

Still open

The other workspace-excluded crates (bgz17, lance-graph-codec-research) were never checked for the same blind spot. Noted in the entry; not swept here.

🤖 Generated with Claude Code

https://claude.ai/code/session_016WkNBjHc2e3zuyz9i8qJEv

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