feat(linters): add stringscountcontains linter

[Copilot]

Adds a new stringscountcontains custom Go analysis linter that flags strings.Count(s, sub) comparisons with 0 or 1 used purely as containment checks. strings.Count walks the entire string while strings.Contains short-circuits on first match — making the latter both clearer in intent and more efficient.

Flagged patterns → suggested fix

// flagged → strings.Contains(s, sub)
strings.Count(s, sub) > 0
strings.Count(s, sub) >= 1
strings.Count(s, sub) != 0
0 < strings.Count(s, sub)   // yoda variants

// flagged → !strings.Contains(s, sub)
strings.Count(s, sub) == 0
strings.Count(s, sub) < 1
strings.Count(s, sub) <= 0
0 == strings.Count(s, sub)  // yoda variants

// not flagged — actual count usage
strings.Count(s, sub) > 2

Changes

• pkg/linters/stringscountcontains/ — new analyzer package; emits SuggestedFix text edits for automated batch repair; respects //nolint:stringscountcontains directives; skips _test.go files
• stringscountcontains_test.go — uses analysistest.RunWithSuggestedFixes with a .go.golden file, consistent with other fix-emitting linters
• cmd/linters/main.go — registered in the multichecker binary
• pkg/linters/README.md — documented in overview list, subpackages table, and import paths section
• pkg/linters/spec_test.go — added to documentedAnalyzers() (39 → 40 documented analyzers)

[github-actions]

PR Triage

Category: feature | Risk: low | Priority: low | Score: 30/100 (impact:15, urgency:5, quality:10) | Action: batch_review | Batch: pr-batch:draft-review

Adds stringscountcontains linter flagging inefficient strings.Count comparisons. Additive/low-risk. Still a draft; no CI yet. Grouped with other draft PRs for batch review.

Generated by 🔧 PR Triage Agent · 31.2 AIC · ⌖ 8.39 AIC · ⊞ 5.4K · ◷