Pin lint tooling and local checks

[marcus]

Summary

• pin local golangci-lint runs to v1.64.8 via a repo-local install target
• replace ad hoc formatting/vet hook logic with shared make targets
• make CI use go.mod's Go version and the same fmt/vet/lint entry points

Verification

• make fmt-check
• make vet
• make lint
• ./scripts/pre-commit.sh
• .git/hooks/pre-commit
• gofmt -l $(git ls-files '*.go')
• ./bin/golangci-lint version --format short
• go test ./... (fails only on pre-existing internal/providers/copilot_test.go:152)

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