feat(noslop): add redundant-comment lens and rename-aware change loading

[Blakeolson21]

What Changed

• Adds a ninth reviewer lens, redundant-comment, backed by a deterministic pre-check in internal/slop/precheck. It lexes Go source with go/scanner and go/parser, groups contiguous comment lines into the comment a reader actually sees, and flags only comment blocks the change added: a phrase restated in the next clause, a doc comment whose every informative word is already spelled by the declaration it documents, and a standalone comment whose words are all present in the adjacent code line. Indented code samples, blank-line-separated notes, and comments carrying constraints or rationale are left alone. The lens is registered in internal/slop/lenses and documented in the taxonomy and README.
• Makes change loading rename-aware. internal/slop/engine/gitload.go switches to --find-renames, carries a new BaselinePath through engine, risk, precheck, and the test floor, derives added/deleted counts from the same diff instead of a second --numstat pass, and demotes a non-identical rename to Modified. internal/git gains Output/OutputBare so blob and NUL-delimited stdout keeps trailing whitespace that Run would trim. The classifier now treats a rename as mechanical only when it preserves path category, extension, and Go build constraints, and scope expansion compares against the baseline path so a relocation is not read as new runtime or schema surface.
• Extends the corpus and scorer. Four new seed cases cover the three redundant-comment shapes plus a clean constraint-comment negative, corpus/results/2026-08-12-r5/ records the round 5 capture, and noslop evaluate gains --case-set with a content-digest manifest (corpus/case-sets/rounds-1-through-4.json) so the pre-expansion baseline and round 4 captures still score against the 32 cases they ran on. Load now accepts an explicit empty expected_findings array for clean negatives.

Pipeline

Updates from git push no-mistakes

⏭️ **intent** - skipped

✅ **Rebase** - passed

✅ **Review** - completed

✅ **Test** - passed

⚠️ **Document** - 1 info

✅ **Lint** - passed

✅ **Push** - passed