audit follow-up PR-A: documentation pass (14 findings)

[oubiwann]

Summary

Closes 14 of 16 findings from PR #15's audit, plus the meta-finding PROMPT-1. No behavioral changes — every edit is a comment, doc, test-helper, or test-table refactor that the substrate flagged. make check (build + lint via golangci-lint + go test -race -count=1 ./...) passes against this branch.

Per the disposition rows in docs/dev/0015-audit-follow-up-plan-address-all-16-findings.md. Single commit per the plan's PR-A scope.

Findings closed

ID	Finding	Resolution
F-1	(AP-02) cite for the string-match-Error rule	→ (AP-13) at pkg/golist/errors.go:16
F-2	EH-08 cite for ctx-ordering rule	→ CC-08 + post-hoc-vs-propagation rationale at pkg/golist/golist.go:204-211
F-3	Same wrong cite at internal/cli/seam.go:62-69	Same fix, mirroring rationale
F-4	ctx-as-last-param rationale	Strengthened inline; PR-C (substrate-align refactor) declined per plan recommendation
F-6	Latent t.Parallel() risk against package-level seams	"Parallel-unsafe" header on 4 seam-test files
F-7	Test-helper duplication (withMetadata vs inline save/restore)	Decline-with-cross-reference in cli_test.go
F-8	internal/cli/helpers_test.go's 8-line writeAll wraps writeFile	Inlined; file deleted
F-9	Inline-map subtest name in golist_test.go:106	Refactored to struct table with name field
F-10	Doc lies post-bug-#12 ("moduleRoot stays empty")	Rewritten to describe actual behaviour at pkg/changeset/changeset.go:65-75
F-11	Same drift in internal comment	Rewritten at changeset.go:113-118
F-12	pkg/ layout vs PS-06 SHOULD-AVOID	Carry-forward note in CLAUDE.md Architecture §
F-13	Dead _ = io.EOF placeholder + comment	Removed at pkg/golist/golist.go
F-15	moduleRootSet exists for test-driven design	Documented at the field declaration
F-16	Mutable build-info globals (AP-07)	"AP-07 deviation (acknowledged)" paragraph at version.go:54-71 (link-time vs runtime; kubectl/hugo/cobra precedent; no t.Parallel())
PROMPT-1	Audit prompt's TD-09 / IM-04 mis-pair	→ IM-12 / TD-09 at workbench/cc-audit-prompt-go-quality.md

S-1 (citation drift, 3 instances + meta): closed.
S-2 (seam pattern + no-t.Parallel() discipline): closed at the doc layer; structural enforcement (custom vet linter) logged as v1.0+ future work.

Diff scope

14 files modified, 1 deleted (internal/cli/helpers_test.go); 120 insertions / 30 deletions. Plan estimated ~25 lines net change; the AP-07 / PS-06 / F-4 doc-strengthen paragraphs make the actual delta larger but still scope-clean.

Test plan

• make check (build + lint + test)
• Spot-check 2-3 cite fixes (F-1, F-2, F-3) against the cited file:line
• Confirm helpers_test.go is gone and writeFile works (test passes)
• Read the F-10/F-11 changeset doc rewrite for accuracy against the actual getCwd + filepath.Abs flow
• Read CLAUDE.md's PS-06 carry-forward note
• gh pr view 15 for the audit + CDC context

Stacking

Base: audit/0014-go-quality-audit (PR #15). After PR #15 merges, this PR's base can be retargeted to main.

PR-B (audit/follow-up-pr-b-cousin-shape, closing F-5 + F-14) is parallel; not stacked on this branch.

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