docs(standards): fix the class, not the instance

[LukasWodka]

Summary

Adds one rule to the Quality bar in org-standards.md:

Fix the class, not the instance. The bug you just fixed is a member of a class; check the rest of the class before you push. Two shapes, and aiming at only the first catches half of them: other call sites — grep the symbol or pattern you changed — and other inputs to the same guard — what else reaches this branch? If the class can't be cheaply enumerated, say so in the PR rather than leaving it implied that you covered it.

Why now

Four defects in a single day shared exactly one root cause — a fix that addressed the instance in front of the author and left the rest of its class:

#	defect	shape
1	a guard wrapped around load(checkout) while discover(root) stayed bare	other call site
2	an epoch-completeness helper used at 2 sites while a 3rd did it inline with a raw non-distinct .count()	other call site
3	a core.hooksPath guard that canonicalised the dirname of the path, not the path — so core.hooksPath=.. escapes it	other input, single site
4	a pre-push hook that probed for make but not for the ruff/pytest toolchain it then calls	other input, single site

Naming both shapes is the point. 1 and 2 are findable by grepping what you changed. 3 and 4 are single-site — a different input reaches the same guard, and no grep of the symbol will ever show you that. A rule phrased only as "check the code nearby" catches half the class, which is precisely how 3 and 4 shipped.

Corroboration from the other direction the same week: a fleet-wide verification script accumulated five defects of this kind, and every one surfaced by running it across all 16 repos rather than by reading the diff (release-train#48). Reviewing a predicate is not the same as enumerating what reaches it.

Scope

Canon only — one line in org-standards.md. The sync (backend#1602) will report the fleet DRIFTED and can open the per-repo CLAUDE.md PRs; per-repo copies are never hand-edited.

Deliberately not in this PR: a matching Sibling check: line in each repo's .github/pull_request_template.md. scripts/standards-sync.py syncs CLAUDE.md only, so templates would be 17 separate PRs — worth doing (a rule that produces an artifact beats one that relies on memory), but it is its own change, and possibly its own extension to the sync script. Filing separately.

Refs backend#1646

🤖 Generated with Claude Code

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Note

Low Risk
Documentation-only change to org engineering standards with no runtime, security, or data-handling impact.

Overview
Quality bar in org-standards.md gains a new bullet: fix the class, not the instance — after a bugfix, enumerate the rest of the same defect class before pushing.

The rule names two shapes reviewers should expect: other call sites (grep the symbol or pattern you changed) and other inputs to the same guard (what else can reach that branch). If the class can't be cheaply enumerated, the PR should say so explicitly instead of implying full coverage.

Canon-only; fleet CLAUDE.md copies follow via the existing standards sync (not edited in this PR).

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